Idempotent route handlers in Next.js, one wrapper

[violetta98]

A dropped connection on the way back from /api/charge means the browser retries, and your handler runs a second time. Route handlers are just Fetch handlers, so this wraps one.

import { InMemoryBackend, withIdempotency } from "idemkit";

export const POST = withIdempotency(
  async (request: Request) => {
    const { amount } = await request.json();
    return Response.json({ chargeId: await charge(amount) }, { status: 201 });
  },
  { backend: new InMemoryBackend() },
);

A retry carrying the same Idempotency-Key replays the first response and never reaches the handler. Node runtime, with Redis, Postgres, Mongo or DynamoDB behind it in production.

Zero dependencies, Apache-2.0: https://github.com/idemkit/idemkit

If you find it useful, a star would be much appreciated.