Freshness and caching

A 15 second snapshot, ETags and 304s.

Read answers come from a snapshot of Payday's books rebuilt every 15 seconds, so asking more often than that returns the same answer. The registry looks for new coins every 3 seconds.

ETags

Every read answer carries an ETag. Send it back as If-None-Match and an unchanged answer comes back as an empty 304 Not Modified, which still counts toward your limit but costs no bandwidth.

curl -i -H "X-API-Key: pd_YOUR_KEY" -H 'If-None-Match: "aB3dE..."' https://payday.direct/api/v1/stats

Cache headers

Keyed answers carry Cache-Control: private, so no shared cache stores them. Keep your own copy for as long as max-age says.