HTTP 304 Not Modified vs 504 Gateway Timeout
HTTP 304 (Not Modified) is a 3xx Redirection response, while 504 (Gateway Timeout) is a 5xx Server Error response. 304 indicates that the resource has not been modified since the last request. The client can use its cached copy. In contrast, 504 means that the server, acting as a gateway or proxy, did not receive a timely response from the upstream server.
Description
The resource has not been modified since the last request. The client can use its cached copy.
When You See It
When the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
How to Fix
No fix needed. This saves bandwidth by confirming the cached version is still current.
Description
The server, acting as a gateway or proxy, did not receive a timely response from the upstream server.
When You See It
When an upstream server is too slow to respond within the proxy's timeout window.
How to Fix
Increase proxy timeout settings. Optimize upstream server performance. Check for long-running queries.
Key Differences
304 is a 3xx Redirection response, while 504 is a 5xx Server Error response.
HTTP 304: The resource has not been modified since the last request. The client can use its cached copy.
HTTP 504: The server, acting as a gateway or proxy, did not receive a timely response from the upstream server.
You encounter 304 when when the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
You encounter 504 when when an upstream server is too slow to respond within the proxy's timeout window.
When to Use Which
For 304 (Not Modified): No fix needed. This saves bandwidth by confirming the cached version is still current. For 504 (Gateway Timeout): Increase proxy timeout settings. Optimize upstream server performance. Check for long-running queries.