The in-memory idx cache kept entries around forever: get() returned
None on expiry but left the HashMap entry in place. Each hourly
HRRR cycle adds ~38 new idx URLs (19 forecast hours × surface +
pressure), so the map grew ~4 MiB/day indefinitely on each Rust
replica. Not the main cause of the OOM loop (glibc fragmentation
was; jemalloc landed last commit) but worth sealing so a long-
lived pod's idx cache can't drift toward the 3 GiB ceiling over
weeks.
Evicts on-touch via `get()` — simple, amortized, no background
sweep thread needed.
Graham McIntire
3ec976ccc4