2.13.c — Zustand: lightweight alternative to heavy Redux

<< 2.13 Overview

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Learning outcomes

1. Create a Zustand store with typed state and actions.
2. Compare Zustand to Context and Redux on complexity and debuggability.
3. Avoid common pitfalls (selector stability, persistence, SSR).

---

Hello store

import { create } from "zustand";

type BearState = {
  bears: number;
  increase: () => void;
};

export const useBearStore = create<BearState>((set) => ({
  bears: 0,
  increase: () => set((state) => ({ bears: state.bears + 1 })),
}));

export function BearCounter() {
  const bears = useBearStore((s) => s.bears);
  const increase = useBearStore((s) => s.increase);
  return (
    <button type="button" onClick={increase}>
      {bears} bears
    </button>
  );
}

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When Zustand often wins

• Medium shared client state without needing Redux DevTools time-travel everywhere.
• Teams wanting minimal boilerplate with good React subscription ergonomics.

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When Redux might still win

• Large org needs strict action logs, replay tooling, and standardized middleware pipelines.
• Heavy cross-team governance already built around Redux Toolkit.

---

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Appendix — Scenario bank (basic → advanced)

Each card: symptom → cause → fix → interview phrase. Drill five cards daily and explain aloud without reading.

GS2-001 — Zustand #1

• Level: Beginner
• Symptom: subtree re-renders 13% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-002 — Zustand #2

• Level: Beginner+
• Symptom: subtree re-renders 26% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-003 — Zustand #3

• Level: Intermediate
• Symptom: subtree re-renders 39% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-004 — Zustand #4

• Level: Intermediate+
• Symptom: subtree re-renders 52% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-005 — Zustand #5

• Level: Advanced
• Symptom: subtree re-renders 65% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-006 — Zustand #6

• Level: Advanced+
• Symptom: subtree re-renders 78% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-007 — Zustand #7

• Level: Beginner
• Symptom: subtree re-renders 91% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-008 — Zustand #8

• Level: Beginner+
• Symptom: subtree re-renders 104% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-009 — Zustand #9

• Level: Intermediate
• Symptom: subtree re-renders 117% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-010 — Zustand #10

• Level: Intermediate+
• Symptom: subtree re-renders 130% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-011 — Zustand #11

• Level: Advanced
• Symptom: subtree re-renders 143% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-012 — Zustand #12

• Level: Advanced+
• Symptom: subtree re-renders 156% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-013 — Zustand #13

• Level: Beginner
• Symptom: subtree re-renders 169% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-014 — Zustand #14

• Level: Beginner+
• Symptom: subtree re-renders 182% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-015 — Zustand #15

• Level: Intermediate
• Symptom: subtree re-renders 195% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-016 — Zustand #16

• Level: Intermediate+
• Symptom: subtree re-renders 8% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-017 — Zustand #17

• Level: Advanced
• Symptom: subtree re-renders 21% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-018 — Zustand #18

• Level: Advanced+
• Symptom: subtree re-renders 34% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-019 — Zustand #19

• Level: Beginner
• Symptom: subtree re-renders 47% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-020 — Zustand #20

• Level: Beginner+
• Symptom: subtree re-renders 60% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-021 — Zustand #21

• Level: Intermediate
• Symptom: subtree re-renders 73% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-022 — Zustand #22

• Level: Intermediate+
• Symptom: subtree re-renders 86% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-023 — Zustand #23

• Level: Advanced
• Symptom: subtree re-renders 99% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-024 — Zustand #24

• Level: Advanced+
• Symptom: subtree re-renders 112% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-025 — Zustand #25

• Level: Beginner
• Symptom: subtree re-renders 125% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-026 — Zustand #26

• Level: Beginner+
• Symptom: subtree re-renders 138% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-027 — Zustand #27

• Level: Intermediate
• Symptom: subtree re-renders 151% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-028 — Zustand #28

• Level: Intermediate+
• Symptom: subtree re-renders 164% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-029 — Zustand #29

• Level: Advanced
• Symptom: subtree re-renders 177% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-030 — Zustand #30

• Level: Advanced+
• Symptom: subtree re-renders 190% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-031 — Zustand #31

• Level: Beginner
• Symptom: subtree re-renders 3% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-032 — Zustand #32

• Level: Beginner+
• Symptom: subtree re-renders 16% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-033 — Zustand #33

• Level: Intermediate
• Symptom: subtree re-renders 29% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-034 — Zustand #34

• Level: Intermediate+
• Symptom: subtree re-renders 42% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-035 — Zustand #35

• Level: Advanced
• Symptom: subtree re-renders 55% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-036 — Zustand #36

• Level: Advanced+
• Symptom: subtree re-renders 68% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-037 — Zustand #37

• Level: Beginner
• Symptom: subtree re-renders 81% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-038 — Zustand #38

• Level: Beginner+
• Symptom: subtree re-renders 94% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-039 — Zustand #39

• Level: Intermediate
• Symptom: subtree re-renders 107% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-040 — Zustand #40

• Level: Intermediate+
• Symptom: subtree re-renders 120% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-041 — Zustand #41

• Level: Advanced
• Symptom: subtree re-renders 133% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-042 — Zustand #42

• Level: Advanced+
• Symptom: subtree re-renders 146% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-043 — Zustand #43

• Level: Beginner
• Symptom: subtree re-renders 159% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-044 — Zustand #44

• Level: Beginner+
• Symptom: subtree re-renders 172% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-045 — Zustand #45

• Level: Intermediate
• Symptom: subtree re-renders 185% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-046 — Zustand #46

• Level: Intermediate+
• Symptom: subtree re-renders 198% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-047 — Zustand #47

• Level: Advanced
• Symptom: subtree re-renders 11% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-048 — Zustand #48

• Level: Advanced+
• Symptom: subtree re-renders 24% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-049 — Zustand #49

• Level: Beginner
• Symptom: subtree re-renders 37% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-050 — Zustand #50

• Level: Beginner+
• Symptom: subtree re-renders 50% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-051 — Zustand #51

• Level: Intermediate
• Symptom: subtree re-renders 63% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-052 — Zustand #52

• Level: Intermediate+
• Symptom: subtree re-renders 76% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-053 — Zustand #53

• Level: Advanced
• Symptom: subtree re-renders 89% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-054 — Zustand #54

• Level: Advanced+
• Symptom: subtree re-renders 102% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-055 — Zustand #55

• Level: Beginner
• Symptom: subtree re-renders 115% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-056 — Zustand #56

• Level: Beginner+
• Symptom: subtree re-renders 128% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-057 — Zustand #57

• Level: Intermediate
• Symptom: subtree re-renders 141% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-058 — Zustand #58

• Level: Intermediate+
• Symptom: subtree re-renders 154% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-059 — Zustand #59

• Level: Advanced
• Symptom: subtree re-renders 167% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-060 — Zustand #60

• Level: Advanced+
• Symptom: subtree re-renders 180% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-061 — Zustand #61

• Level: Beginner
• Symptom: subtree re-renders 193% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-062 — Zustand #62

• Level: Beginner+
• Symptom: subtree re-renders 6% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-063 — Zustand #63

• Level: Intermediate
• Symptom: subtree re-renders 19% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-064 — Zustand #64

• Level: Intermediate+
• Symptom: subtree re-renders 32% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-065 — Zustand #65

• Level: Advanced
• Symptom: subtree re-renders 45% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-066 — Zustand #66

• Level: Advanced+
• Symptom: subtree re-renders 58% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-067 — Zustand #67

• Level: Beginner
• Symptom: subtree re-renders 71% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-068 — Zustand #68

• Level: Beginner+
• Symptom: subtree re-renders 84% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-069 — Zustand #69

• Level: Intermediate
• Symptom: subtree re-renders 97% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-070 — Zustand #70

• Level: Intermediate+
• Symptom: subtree re-renders 110% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-071 — Zustand #71

• Level: Advanced
• Symptom: subtree re-renders 123% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-072 — Zustand #72

• Level: Advanced+
• Symptom: subtree re-renders 136% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-073 — Zustand #73

• Level: Beginner
• Symptom: subtree re-renders 149% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-074 — Zustand #74

• Level: Beginner+
• Symptom: subtree re-renders 162% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-075 — Zustand #75

• Level: Intermediate
• Symptom: subtree re-renders 175% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-076 — Zustand #76

• Level: Intermediate+
• Symptom: subtree re-renders 188% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-077 — Zustand #77

• Level: Advanced
• Symptom: subtree re-renders 1% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-078 — Zustand #78

• Level: Advanced+
• Symptom: subtree re-renders 14% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-079 — Zustand #79

• Level: Beginner
• Symptom: subtree re-renders 27% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-080 — Zustand #80

• Level: Beginner+
• Symptom: subtree re-renders 40% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-081 — Zustand #81

• Level: Intermediate
• Symptom: subtree re-renders 53% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-082 — Zustand #82

• Level: Intermediate+
• Symptom: subtree re-renders 66% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-083 — Zustand #83

• Level: Advanced
• Symptom: subtree re-renders 79% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-084 — Zustand #84

• Level: Advanced+
• Symptom: subtree re-renders 92% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-085 — Zustand #85

• Level: Beginner
• Symptom: subtree re-renders 105% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-086 — Zustand #86

• Level: Beginner+
• Symptom: subtree re-renders 118% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-087 — Zustand #87

• Level: Intermediate
• Symptom: subtree re-renders 131% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-088 — Zustand #88

• Level: Intermediate+
• Symptom: subtree re-renders 144% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-089 — Zustand #89

• Level: Advanced
• Symptom: subtree re-renders 157% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-090 — Zustand #90

• Level: Advanced+
• Symptom: subtree re-renders 170% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-091 — Zustand #91

• Level: Beginner
• Symptom: subtree re-renders 183% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-092 — Zustand #92

• Level: Beginner+
• Symptom: subtree re-renders 196% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-093 — Zustand #93

• Level: Intermediate
• Symptom: subtree re-renders 9% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-094 — Zustand #94

• Level: Intermediate+
• Symptom: subtree re-renders 22% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-095 — Zustand #95

• Level: Advanced
• Symptom: subtree re-renders 35% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-096 — Zustand #96

• Level: Advanced+
• Symptom: subtree re-renders 48% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-097 — Zustand #97

• Level: Beginner
• Symptom: subtree re-renders 61% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-098 — Zustand #98

• Level: Beginner+
• Symptom: subtree re-renders 74% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-099 — Zustand #99

• Level: Intermediate
• Symptom: subtree re-renders 87% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-100 — Zustand #100

• Level: Intermediate+
• Symptom: subtree re-renders 100% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-101 — Zustand #101

• Level: Advanced
• Symptom: subtree re-renders 113% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-102 — Zustand #102

• Level: Advanced+
• Symptom: subtree re-renders 126% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-103 — Zustand #103

• Level: Beginner
• Symptom: subtree re-renders 139% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-104 — Zustand #104

• Level: Beginner+
• Symptom: subtree re-renders 152% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-105 — Zustand #105

• Level: Intermediate
• Symptom: subtree re-renders 165% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-106 — Zustand #106

• Level: Intermediate+
• Symptom: subtree re-renders 178% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-107 — Zustand #107

• Level: Advanced
• Symptom: subtree re-renders 191% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-108 — Zustand #108

• Level: Advanced+
• Symptom: subtree re-renders 4% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-109 — Zustand #109

• Level: Beginner
• Symptom: subtree re-renders 17% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-110 — Zustand #110

• Level: Beginner+
• Symptom: subtree re-renders 30% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-111 — Zustand #111

• Level: Intermediate
• Symptom: subtree re-renders 43% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-112 — Zustand #112

• Level: Intermediate+
• Symptom: subtree re-renders 56% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-113 — Zustand #113

• Level: Advanced
• Symptom: subtree re-renders 69% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-114 — Zustand #114

• Level: Advanced+
• Symptom: subtree re-renders 82% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-115 — Zustand #115

• Level: Beginner
• Symptom: subtree re-renders 95% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-116 — Zustand #116

• Level: Beginner+
• Symptom: subtree re-renders 108% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-117 — Zustand #117

• Level: Intermediate
• Symptom: subtree re-renders 121% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-118 — Zustand #118

• Level: Intermediate+
• Symptom: subtree re-renders 134% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-119 — Zustand #119

• Level: Advanced
• Symptom: subtree re-renders 147% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-120 — Zustand #120

• Level: Advanced+
• Symptom: subtree re-renders 160% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-121 — Zustand #121

• Level: Beginner
• Symptom: subtree re-renders 173% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-122 — Zustand #122

• Level: Beginner+
• Symptom: subtree re-renders 186% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-123 — Zustand #123

• Level: Intermediate
• Symptom: subtree re-renders 199% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-124 — Zustand #124

• Level: Intermediate+
• Symptom: subtree re-renders 12% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-125 — Zustand #125

• Level: Advanced
• Symptom: subtree re-renders 25% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-126 — Zustand #126

• Level: Advanced+
• Symptom: subtree re-renders 38% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-127 — Zustand #127

• Level: Beginner
• Symptom: subtree re-renders 51% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-128 — Zustand #128

• Level: Beginner+
• Symptom: subtree re-renders 64% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-129 — Zustand #129

• Level: Intermediate
• Symptom: subtree re-renders 77% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-130 — Zustand #130

• Level: Intermediate+
• Symptom: subtree re-renders 90% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-131 — Zustand #131

• Level: Advanced
• Symptom: subtree re-renders 103% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-132 — Zustand #132

• Level: Advanced+
• Symptom: subtree re-renders 116% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-133 — Zustand #133

• Level: Beginner
• Symptom: subtree re-renders 129% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-134 — Zustand #134

• Level: Beginner+
• Symptom: subtree re-renders 142% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-135 — Zustand #135

• Level: Intermediate
• Symptom: subtree re-renders 155% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-136 — Zustand #136

• Level: Intermediate+
• Symptom: subtree re-renders 168% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-137 — Zustand #137

• Level: Advanced
• Symptom: subtree re-renders 181% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-138 — Zustand #138

• Level: Advanced+
• Symptom: subtree re-renders 194% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-139 — Zustand #139

• Level: Beginner
• Symptom: subtree re-renders 7% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-140 — Zustand #140

• Level: Beginner+
• Symptom: subtree re-renders 20% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-141 — Zustand #141

• Level: Intermediate
• Symptom: subtree re-renders 33% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-142 — Zustand #142

• Level: Intermediate+
• Symptom: subtree re-renders 46% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-143 — Zustand #143

• Level: Advanced
• Symptom: subtree re-renders 59% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-144 — Zustand #144

• Level: Advanced+
• Symptom: subtree re-renders 72% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-145 — Zustand #145

• Level: Beginner
• Symptom: subtree re-renders 85% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-146 — Zustand #146

• Level: Beginner+
• Symptom: subtree re-renders 98% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-147 — Zustand #147

• Level: Intermediate
• Symptom: subtree re-renders 111% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-148 — Zustand #148

• Level: Intermediate+
• Symptom: subtree re-renders 124% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-149 — Zustand #149

• Level: Advanced
• Symptom: subtree re-renders 137% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-150 — Zustand #150

• Level: Advanced+
• Symptom: subtree re-renders 150% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-151 — Zustand #151

• Level: Beginner
• Symptom: subtree re-renders 163% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-152 — Zustand #152

• Level: Beginner+
• Symptom: subtree re-renders 176% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-153 — Zustand #153

• Level: Intermediate
• Symptom: subtree re-renders 189% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: SSR hydration mismatch because client-only default differs from server snapshot.
• Primary remediation: Gate client defaults behind useEffect or align SSR snapshot with same initial state.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-154 — Zustand #154

• Level: Intermediate+
• Symptom: subtree re-renders 2% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Persist middleware misused storing sensitive tokens in localStorage.
• Primary remediation: Export singleton store from module scope; document HMR patterns.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-155 — Zustand #155

• Level: Advanced
• Symptom: subtree re-renders 15% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Selectors return new objects each call causing unnecessary React updates.
• Primary remediation: Extract pure reducers/helpers testable without React.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-156 — Zustand #156

• Level: Advanced+
• Symptom: subtree re-renders 28% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Store becomes a junk drawer of unrelated keys with no module ownership.
• Primary remediation: Partition stores or use slices with clear names; enforce ADR ownership per slice.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-157 — Zustand #157

• Level: Beginner
• Symptom: subtree re-renders 41% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Business rules embedded in setter lambdas without tests.
• Primary remediation: Use shallow compare or return primitives from selectors; use useShallow when appropriate.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

GS2-158 — Zustand #158

• Level: Beginner+
• Symptom: subtree re-renders 54% more than expected after a small unrelated UI change.
• Architecture smell: unclear ownership of who may mutate shared state.
• Root cause class: Multiple store instances created accidentally in dev strict or HMR edge cases.
• Primary remediation: Never persist secrets; whitelist keys; encrypt only when product requires and experts agree.
• Proof: React DevTools highlight updates; split providers and re-measure.
• Interview one-liner: Zustand trades ceremony for discipline—you still need boundaries and conventions.

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