Caches the origin's error responses to decrease server load. Applies for 10 seconds by default to the following HTTP codes: 204, 305, 404, 405, 501, 502, 503, 504, and 505.

This behavior no longer caches 400 error responses from the origin server. If you need to cache such errors, you can set up a custom variable. See Caching 400 responses for more information.


Activates the error-caching behavior.

ttlstring (duration)

Overrides the default caching duration of 10s. Note that if set to 0, it is equivalent to no-cache, which forces revalidation and may cause a traffic spike. This can be counterproductive when, for example, the origin is producing an error code of 500.


When enabled, the edge server preserves stale cached objects when the origin returns 500, 502, 503, and 504 error codes. This avoids re-fetching and re-caching content after transient errors.