Redis evicting security tokens
Redis ships with an eviction maxmemory-policy, so under memory pressure it silently drops rate-limit counters and tokens. Switched to noeviction with a CI smoke test.
It said it worked
Green, 200, saved, “already handled” — and wrong. No error anywhere to go on.
The default maxmemory-policy is an eviction policy. Under memory pressure Redis would silently drop a rate-limit counter or a token — no error, no log, just a security control that stops existing for a while. Switched to noeviction, and there's a CI smoke test asserting it now, because this is exactly the setting a future config cleanup reverts with no visible symptom.
Same commit fixed a related annoyance: a transient Redis blip was flipping /health to unhealthy, which got Docker to kill a perfectly healthy container.