HTTP Status Codes Error 504: Gateway Timeout

Identify: does your log match?

HTTP/1.1 504 Gateway Time-out
Server: nginx/1.27.2

2026/10/22 13:12:09 [error] 31#31: *2210 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 172.18.0.1, server: api.example.com, request: "POST /v1/reports HTTP/1.1", upstream: "http://172.18.0.5:3000/v1/reports"

1. High

   Slow query or external call

   The handler waits on an unindexed query or a slow third-party API longer than the proxy timeout.

2. Medium

   Synchronous long-running job

   Reports, exports or video processing done in the request path will always exceed gateway limits under load.

3. Medium

   Upstream saturated

   All workers are busy; requests queue in the app until the proxy gives up.

Fix

app.post('/v1/reports', async (req, res) => {
  const file = await buildReport(req.body); // 90s
  res.json({ url: file.url });
});

app.post('/v1/reports', async (req, res) => {
  const job = await queue.add('report', req.body);
  res.status(202).location(`/v1/reports/${job.id}`).json({ id: job.id, status: 'queued' });
});

app.get('/v1/reports/:id', async (req, res) => {
  const job = await queue.getJob(req.params.id);
  res.json({ status: await job.getState(), url: job.returnvalue?.url });
});

Verify: reproduce it on purpose

$ curl -i --max-time 5 https://httpbin.org/delay/10

Prevent

• Set app-level timeouts below the gateway timeout.
• Measure p99 latency per route.
• Use a job queue for anything > 10 s.