mir-backend-node-expresslisted

Make It Right (Express module). Express 4/5 + Node.js specific reliability augmentation. Use alongside mir-backend and mir-backend-node when the target stack is Express — it carries the mechanical footguns that the framework-agnostic tiers deliberately omit: async error propagation differences between Express 4 and 5, middleware ordering as a hard contract, the absence of built-in validation and what fills the gap, security headers and CORS off-by-default, and object-level authorization gaps that structural frameworks catch but Express doesn't. TRIGGER only when the Node backend stack is Express — building, reviewing, or debugging an Express route, middleware, or error handler. Always loads TOGETHER WITH mir-backend (the gates) and mir-backend-node (V8 event-loop / process-model concerns: blocking, worker_threads, unhandled rejections, backpressure, timeouts); this module only adds Express library mechanics. SKIP for Fastify, NestJS, Hapi, Koa, or any non-Express stack (those get their own mir-backend-node-<f
anantbhandarkar/make-it-right · ★ 12 · API & Backend · score 83

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# /mir-backend-node-express · Make It Right (Express) Bottom tier of the chain: `mir-backend` (generic gates) → `mir-backend-node` (V8/Node event-loop model) → **this** (Express library mechanics). Run the gates first; load the Node runtime tier for event-loop and process-model concerns; reach for *this* at Gate 5 (design mechanics), Gate 6 (implementation), and Gate 7 review. **Runtime-level concerns (blocking the event loop, worker_threads, unhandled rejections, stream backpressure, AbortController timeouts, heap limits) live in `mir-backend-node` — not here.** **Stack assumed:** Express 4.x or 5.x on Node 20+ LTS. Version differences that change behavior are called out explicitly. ## The Express footguns AI walks into most ### 1. Async errors in Express 4 are silently swallowed — Express 5 changes this This is the single most common Express reliability defect AI ships. **Express 4** does not await route handler return values. If an `async` handler throws, the error is an unhandled promise rejection — it does **not** reach your `(err, req, res, next)` error handler, and the request hangs until the client times out: ```js // WRONG in Express 4 — thrown error is an unhandled rejection, request hangs app.get('/users/:id', async (req, res) => { const user = await db.findUser(req.params.id); // throws → disappears res.json(user); }); ``` Fix: wrap with a helper that forwards rejections to `next`, or explicitly catch and call `next(err)`: ```js // Option A — asyncHan