{"library":"express-idempotency-middleware","type":"library","category":null,"description":"Express middleware for idempotent POST requests using Idempotency-Key header (version 1.0.2, stable release, active development). Provides pluggable stores (Memory, Redis, Postgres), in-flight concurrency control with wait or reject strategies, and safe response replay with header whitelist. TypeScript-first, ESM-only, requires Node ≥18 and Express 4 or 5. Differentiators: built-in in-flight handling via wait timeout polling, stable response fingerprinting, and separate replay header whitelist for security-aware caching of location headers without cookies or auth tokens. Designed for payment, order, and webhook idempotency scenarios.","language":"javascript","status":"active","version":"1.0.2","tags":["javascript","express","middleware","idempotency","idempotent","api","webhooks","payments","typescript"],"last_verified":"Wed May 27","install":[{"cmd":"npm install express-idempotency-middleware","imports":["import { idempotencyMiddleware } from 'express-idempotency-middleware'","import { MemoryStore } from 'express-idempotency-middleware'","import type { IdemOptions } from 'express-idempotency-middleware'"]},{"cmd":"yarn add express-idempotency-middleware","imports":[]},{"cmd":"pnpm add express-idempotency-middleware","imports":[]}],"homepage":null,"github":"https://github.com/YevhenMykhailenko/idempotency-express","docs":null,"changelog":null,"pypi":null,"npm":"https://www.npmjs.com/package/express-idempotency-middleware","openapi_spec":null,"status_page":null,"smithery":null,"compatibility":{"summary":{"python_range":"18–22","success_rate":0,"avg_install_s":null,"avg_import_s":null,"wheel_type":null},"url":"https://checklist.day/v1/registry/express-idempotency-middleware/compatibility"}}