Error pages should set an appropriate HTTP status code: 4xx for client errors such as invalid requests and 5xx for server errors.
HTTP error codes will prevent upstream components from caching the response. Heavyweight error pages which rely on upstream response caching should therefore be avoided.
Invalid requests should be detected early and be rejected quickly, without spending much CPU resources on them.
For security reasons, error messages and error pages should not reveal information about the application or its infrastructure. For instance, avoid sending stack traces to untrusted users.
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