Route Precedence

1// Express — first registered match wins
2app.get('/users/:id', getUser)   // registered first
3app.get('/users/me', getMe)      // dead code: never reached
4// GET /users/me  ->  getUser with req.params.id === 'me'
5 
6// Fix: literal before parametric
7app.get('/users/me', getMe)
8app.get('/users/:id', getUser)
9 
10 
11// Fastify — radix trie, static segment beats parametric
12fastify.get('/users/:id', getUser)
13fastify.get('/users/me', getMe)   // order irrelevant
14// GET /users/me  ->  getMe
15 
16// Go 1.22+ — most specific pattern wins; ambiguity panics
17mux.HandleFunc("GET /users/{id}", getUser)
18mux.HandleFunc("GET /users/me", getMe)   // order irrelevant
19// mux.HandleFunc("GET /a/{x}/c", h1); mux.HandleFunc("GET /a/b/{y}", h2)
20// -> panic at registration: neither is more specific than the other

The Express fix is a line order. The Fastify and Go versions have no fix because there is no bug. That difference is the whole lesson: identical route definitions, different behaviour, and only one of the three tells you.

// routes are grouped by resource and read nicely
app.use(express.static('public'))     // catch-all, registered first
app.get('/orders/:id', getOrder)
app.get('/orders/summary', summary)  // shadowed, silently dead
app.use(apiRouter)                    // never reached for /orders/*

const CASES = [
  ['GET',  '/orders/summary', 'summary'],
  ['GET',  '/orders/4711',   'getOrder'],
  ['GET',  '/api/missing',   '404'],       // not the SPA fallback
  ['POST', '/orders/4711',   '405'],
] as const

for (const [method, path, expected] of CASES) {
  it(`${method} ${path} -> ${expected}`, async () => {
    const res = await request(app)[method.toLowerCase()](path)
    expect(res.headers['x-matched-route']).toBe(expected)
  })
}

Reading gives you an opinion about resolution; the table gives you a fact, and it keeps being a fact after someone reorders imports, adds a mount, or upgrades the router. The /api/missing case is the one that matters most — it asserts that the SPA fallback does not swallow API 404s.