504 Gateway Timeout: Meaning, Causes and Fixes

What 504 means

The proxy reached the application, but the application did not respond within the proxy's timeout (nginx proxy_read_timeout, default 60 s; cloud load balancers often 30–60 s). The request may still be running on the backend after the client sees 504.

It usually points at a slow query, an external API call without a timeout, or a request that should have been made asynchronous.

Common causes

Slow database query or lock contention.
Outbound call to a third-party API hanging.
CPU-starved application under load.
Long-running export or report served synchronously.

How to fix it

Find the slow request in the application logs or APM and fix the query or add a timeout to the outbound call.
Move long work behind a job queue and return 202.
Only raise the proxy timeout when the operation genuinely needs longer, and align every layer (CDN, LB, proxy, app).

What it looks like

A typical response:

HTTP/1.1 504 Gateway Timeout
Server: nginx
Content-Type: text/html

<html><head><title>504 Gateway Time-out</title></head>…

The same event in an nginx access log (the status is the number after the request line):

203.0.113.7 - - [10/Sep/2026:10:12:01 +0000] "GET /api/report HTTP/1.1" 504 153 "-" "Mozilla/5.0"

Check it with curl

-i prints the status line and headers, and -w '%{http_code}' prints only the number, which is handy in scripts and health checks. Replace the URL with yours:

curl -sS -o /dev/null -w '%{http_code} %{time_total}s\n' https://example.com/api/orders

Compare what curl sees with what the browser sees. A different status from the same URL usually means a cache, a CDN edge or a cookie is in the way.

Investigating a run of 504s? Paste the log excerpt into Log Share to get line numbers, highlighting and an expiring link for whoever is on call with you.

502Bad Gateway: A proxy or load balancer got an invalid response from the upstream server.
503Service Unavailable: The server is temporarily unable to handle the request.
408Request Timeout: The client took too long to send the request.

FAQ

Why does my request time out at exactly 60 seconds?

That is the default proxy_read_timeout in nginx and a common load balancer idle timeout. The backend is slower than that; fixing the backend beats raising the timeout.

Is the backend still working after a 504?

Often yes. The proxy dropped the connection, but the application may complete the work, which is why non-idempotent requests must not be retried blindly.

504 Gateway Timeout