Cache Behaviors and TTLs
~10 min read
How CloudFront decides what to cache, for how long, and what makes two requests 'the same' for caching purposes.
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Key points
- •Cache behaviors are matched by URL path pattern, most specific pattern wins
- •The cache key determines what counts as 'the same request' — by default excludes query strings/headers/cookies
- •TTLs can be set explicitly in CloudFront or driven by the origin's Cache-Control/Expires headers
- •Including unnecessary elements in the cache key fragments the cache and hurts hit rate