Caching

The router caches hot reads in process so repeated requests avoid re-reading static files. Cache is scoped to a single instance (no shared external store).

Layers

Layer	Behavior
Cache	Keyed by static path; default 512 entries / 256 MB
TTL	Default 300s for payloads, 60s for negative (404) entries
Request coalescing	Concurrent misses for the same key share one load
Version poll	Every 10 minutes, reads version.json; if export_date changes, the cache is cleared

Response headers

• ETag — weak FNV-1a of the response body (stable across processes)
• If-None-Match — returns 304 Not Modified on match
• X-Cache: HIT|MISS
• Cache-Control: public, max-age=… (+ s-maxage) on JSON routes; /health is private, no-store
• Vary: origin, accept-encoding

Configuration (env)

Variable	Default	Meaning
CACHE_MAX_ENTRIES	512	max cached entries
CACHE_MAX_BYTES	268435456	approx memory cap
CACHE_TTL_MS	300000	positive TTL
CACHE_NEGATIVE_TTL_MS	60000	404 TTL
VERSION_POLL_MS	600000	export version poll interval

Multi-instance deployments keep independent in-process caches and converge via TTL + version polling.