2.20 — Quick Revision: Next.js APIs

<< 2.20 Overview

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Cheat Sheet

Topic	Remember
File	app/.../route.ts
Exports	GET, POST, PUT, PATCH, DELETE, …
Request	Web Request / NextRequest
Response	NextResponse.json(body, { status, headers })
Query	request.nextUrl.searchParams
Dynamic	context.params — await in Next 15+
JSON body	await request.json() in try/catch → 400 if invalid
Validation	Zod → 422 or 400 (pick one, document)
DB	Service layer + pooled / serverless-safe connection
Delete ok	204 + empty body common pattern

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2.20.a — Route handlers & conventions

• Folder path under app/ defines URL segments; route.ts collocates HTTP with UI routes if you choose.
• Prefer route.ts over legacy pages/api for new App Router projects.

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2.20.b — HTTP methods

• One export per verb; return precise status codes; document idempotency for PUT/DELETE.
• Parse query params from NextRequest#nextUrl.

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2.20.c — Databases

• Handlers stay thin; services/transactions live in modules callable from actions too.
• Watch serverless connection storms; use poolers/proxies recommended by your ORM.

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2.20.d — Response shape & errors

• Stable code, safe message, optional details for fields.
• Log rich diagnostics server-side with request correlation ids.

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Status Codes (Ultra Short)

200 OK          — read / update with body
201 Created     — POST create
204 No Content  — delete / update no body
400             — bad JSON / bad request
401 / 403       — authn / authz
404             — missing resource
409             — conflict
500             — unexpected (log inside)

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One-Line Senior Phrase

“route.ts is the HTTP adapter; services own business logic and transactions; errors map to stable codes and safe messages.”

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Self-check: spoken answers

#	Prompt	Answer you should produce
1	Where does GET /api/health live?	app/api/health/route.ts exporting GET.
2	Pages api vs route.ts?	Legacy default handler vs App Router per-verb Web APIs.
3	Malformed JSON status?	400 after failed request.json() parse.
4	Duplicate unique constraint?	409 with stable code like EMAIL_IN_USE.
5	Why service layer?	Testability, reuse from Server Actions, centralized transactions.
6	Edge DB caution?	Driver support + pooling model; default Node for classic SQL unless proven.
7	CORS with cookies?	Never careless *; explicit origin allowlist + correct preflight.
8	When Route Handler over Server Action?	Public HTTP consumers, webhooks, documented REST/OpenAPI needs.

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<< 2.20 Overview