Header Preservation

@express-route-cache ensures that your cached responses are high-fidelity replays of the original, including all relevant HTTP headers.

Automatic Preservation

The following are automatically captured and replayed:

• CORS Headers: Access-Control-Allow-Origin, etc.
• Content-Type: Ensures the client knows how to parse the data.
• Custom Headers: Any headers your middleware or handlers set.

Excluded Headers

We intentionally strip ephemeral or session-specific headers to prevent security issues or incorrect behavior:

• Set-Cookie
• X-Express-* internal headers
• Connection, Keep-Alive, etc.

Cache Visibility Headers

We add our own headers to help you debug and monitor cache performance:

• X-Cache: HIT | MISS | STALE
• Age: Time in seconds since the cache entry was created.
• Cache-Control: Automatically calculated based on your staleTime.

Customizing Cache Identity (vary)

If your response changes based on a header (like Authorization or Accept-Language), use the vary option:

const cache = createCache({
  vary: ['authorization', 'accept-language'],
});

This ensures that different users get their own private cached versions of the data.