Field note 04

Observing Cache Behavior

Repeat requests reveal useful details when the response carries explicit validators.

Choose a stable validator

An ETag or Last-Modified value gives the client a clear way to ask whether a resource changed. Record the first response and the conditional request separately.

Separate cache layers

A browser cache, shared edge cache and application cache can produce similar outcomes for different reasons. Timing alone rarely identifies the responsible layer.

Document freshness

Cache-Control directives explain the intended freshness policy. Observed behavior should be compared with that policy rather than with an unstated assumption.

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