@api-profiler/express

See how fast your Express routes actually are — measured on real requests, never guessed — and replay a recorded request under load with one call.

npm install @api-profiler/express

const express = require('express');
const { profiler } = require('@api-profiler/express');

const app = express();
const p = profiler();
app.use(p);            // before your routes

app.listen(3000);

That is all. Send a few requests, then either:

• open the terminal: npx api-profiler (package api-profiler) for a live table;
• install the API Performance Profiler VS Code extension to see 🟢 84ms at the end of each route line, and a ▶ Load test lens above it;
• read the figures in code: p.stats().

What it measures

Per route (GET /users/:id, as written in your code) for the last 5 seconds: request count, average and max latency, error rate, and requests per second once there are enough samples. Observed traffic and generated load are kept apart and always labelled.

Load testing

Locally, the profiler keeps the most recent successful request per route in memory — URL, headers (auth included) and body — so it can replay it:

const result = await p.loadTest('GET', '/users/:id');   // 10 connections × 5s
result.stats;   // the route's own server-side figures for the run

Rules that never bend: off in production, localhost targets only, GET only unless you opt a route in with profiler({ allowLoadOn: ['POST /search'] }) (replaying a POST writes real data). Every replayed request carries x-api-profiler-load: 1 so handlers can skip mail, payments and the like.

Privacy

Recordings hold live credentials. They stay in memory, are never written to disk or sent anywhere, and are masked wherever they are shown. With NODE_ENV=production nothing is recorded at all. Set NODE_ENV=production on your servers: an unset NODE_ENV counts as development.

In development a small JSON server opens on http://127.0.0.1:4780 (loopback only) for the CLI and the extension. profiler({ channel: false }) turns it off, profiler({ channel: { port: 4790 } }) moves it.

Options

profiler({
  windowMs: 5000,                 // rolling window for the figures
  allowLoadOn: ['POST /search'],  // non-GET routes that may be replayed
  channel: { port: 4780 },        // or false
});

Works with Express 4 and 5, Node 18+. Zero overhead on the request path beyond a timer and one in-memory update.

Licence

AGPL-3.0-only. Source and issues: https://github.com/Nahid625/api-performance-profiler