Example HTTP Response
HTTP/1.1 504 Gateway Timeout- Upstream server too slow
- Network issues between servers
- Backend request processing timeout
What does this mean?
The middleman gave up waiting! The proxy knocked on the backend's door but nobody answered in time.
Technical Definition
The server was acting as a gateway and could not get a response in time.
RFC Says
"The 504 (Gateway Timeout) status code indicates that the server, while acting as a gateway or proxy, did not receive a timely response from an upstream server it needed to access in order to complete the request."
Plain English:
504 means 'I'm a proxy/gateway, and the server behind me took too long to respond, so I gave up.' This happens when a reverse proxy has a timeout (say 60 seconds) and your application server doesn't respond within that time. Unlike 408 (client took too long), 504 means the backend took too long.
Common Misinterpretation
Like 502, this should come from infrastructure (proxies, load balancers, API gateways), not your application code. If your app times out waiting for a database or external API, consider returning 500 or 503 instead. 504 specifically means a proxy gave up waiting for an upstream server.
Ready-to-use code for returning this HTTP status in your application:
// Express.js
app.get('/example', (req, res) => {
res.status(504).json({
error: 'Gateway Timeout',
message: 'Your error message here'
});
});
// Native HTTP
const http = require('http');
http.createServer((req, res) => {
res.writeHead(504, { 'Content-Type': 'application/json' });
res.end(JSON.stringify({
error: 'Gateway Timeout',
message: 'Your error message here'
}));
}).listen(3000);- Proxy/gateway timed out waiting for upstream server
- Backend server is taking too long to respond
- Use when acting as gateway and upstream doesn't respond in time
- Use 408 for client request timeout, 504 for gateway timeout