Koa guide · Node.js SDK

Koa rate limiting,keyed to paying customers.

One app.use() checks the caller’s API key, charges their credits, and holds them to their plan’s limit before the rest of your middleware runs.

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  • Keys issued per customer
  • Credits that refill
  • Limits per plan, not per process

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The usual Koa rate limiter counts requests. It doesn’t know your customers.

koa-ratelimit counts requests per id function with a memory Map or Redis driver, and sets rate-limit headers on the response.

With koa-ratelimittoday
// server.ts — with koa-ratelimitimport ratelimit from "koa-ratelimit";

const db = new Map();

app.use(
  ratelimit({
    driver: "memory",
    db,
    duration: 60000,
    max: 100,
    id: (ctx) => ctx.get("x-api-key") || ctx.ip,
  }),
);
  • Counters live in process memory — every worker and every instance keeps its own count
  • Needs Redis (or another shared store) before the limit is correct on more than one server
  • No API keys: issuing, hashing, scoping, and revoking them is still yours to build
  • No credit balance: a request can’t cost 5 on one route and 1 on another, or refill each month
  • One limit for everyone — no per-plan limits for Free, Pro, and Enterprise customers
  • No per-customer usage log to answer “why was I blocked?” or bill against
With ReqKey in Koaone middleware
  • API keys issued per customer, prefixed, hashed, and revocable from the dashboard
  • A credit balance per customer — price each route, refill every hour, day, week, or month
  • Rate limits set per plan, shared by all of a customer’s keys, from 1 second to 24 hours
  • The same count on every worker, instance, and region — no Redis to run
  • Over the limit? A 429 with Retry-After, and no credits charged
  • Every request logged per customer — status, latency, endpoint — in under 5ms
Downstream middleware reads the verdict from ctx.state.reqkey. See the code

Koa in three steps, one of them code.

ReqKey runs inside your API, not in front of it. Your server asks one question per request and gets an answer in under 5ms.

  1. 1

    Install the SDK

    npm install reqkey koa

  2. 2

    Set your project key

    Copy it from the dashboard into REQKEY_PROJECT_KEY. It stays on your server.

  3. 3

    Add the Koa middleware

    Every request is checked, charged, and logged before your handler runs.

server.tsnpm install reqkey koa
import Koa from "koa";
import reqkey from "reqkey/koa";
 
const app = new Koa();
 
app.use(
  reqkey({
    projectKey: process.env.REQKEY_PROJECT_KEY,
    apiId: "api_payments",
    mode: "both",
    keyName: "x-startup-key",
    excludePaths: ["/health"],
  }),
);
 
app.use((context) => {
  context.status = 201;
  context.body = { created: true, creditsRemaining: context.state.reqkey?.creditsRemaining };
});
 
app.listen(3000);
Also in Node.js: Express, Next.js, NestJS, Fastify, HonoFull Node.js reference

Every request gets one of these answers

  • 200Valid key, credits charged — your handler runs
  • 402Out of credits
  • 403Key disabled, or not allowed on this API
  • 429Over the rate limit — no credits charged

Where ReqKey sits

Your customer
Your APIReqKey, under 5ms
Your handler

Responses go straight back to your customer. ReqKey sees the key check and the log line, nothing else.

Credits

Charge each route what it costs you.

A lookup can cost 1 credit and a render 5, from the same balance. Excluded paths are never validated, charged, or recorded. In Node.js:

Per-route credits · Node.js
// Exact paths or trailing-* prefixes: never validated, charged, or recorded
excludePaths: ["/health", "/openapi.json", "/docs/*", "/cron/*"]
 
// Or decide per request with a sync or async resolver
shouldProtect: ({ path }) => path.startsWith("/api/")
 
// Charge different endpoints differently (non-negative integers)
credits: ({ method, path }) => {
  if (method === "POST" && path === "/images") return 5;
  if (path.startsWith("/reports/")) return 2;
  return 1;
}

Rate limits

Set limits on plans, not in code.

Your Koa code never hard-codes a number. Each plan carries its credits, refill, and rate limit; moving a customer to Pro changes all three with no deploy.

PlanCreditsRate limit
Free1,000 / month5 req / s
Pro50,000 / month50 req / s
Scale1,000,000 / month500 req / s
429Over the limit, a call is answered with Retry-After and costs nothing — no credits and no quota.

Example plans. You name them and pick the numbers.

Notes for Koa teams hit in production.

Fits the onion

Put reqkey() first and every middleware below it only runs for valid, in-credit, in-limit requests.

State you can read

ctx.state.reqkey carries credits remaining, the consumer, and the request ID for logging or response bodies.

Open paths stay open

excludePaths skips health checks and docs entirely — never validated, charged, or recorded.

Koa rate limiting: the questions teams ask.

Something else? Ask the team or read the docs.

  • Near the top, before routers, so rejected requests never reach your handlers.

  • The request is answered with a 402 before your handlers run. Top up their balance, or let the plan’s refill restore it.

  • On their plan or on the customer (consumer) in ReqKey — a number of requests per window from 1 second to 24 hours, shared by all of that customer’s keys. Your Koa code never hard-codes a limit, so upgrading a customer is a dashboard change, not a deploy.

  • A check averages under 5ms. ReqKey runs inside your app as middleware, not as a gateway in front of it, so responses go straight back to your customer.

  • You choose: fail closed and answer 503, or fail open and let requests through. Invalid keys are denied either way, and a validation is never retried, so no one is charged twice.

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