Health check flapping
An L7 load balancer is flapping backends in and out of rotation every 20-40 seconds. The dashboard shows the healthy-host count for one target group oscillating between 12 and 30 (of 30), and clients see intermittent 503s with elevated tail latency. Per-host metrics look fine: CPU ~55%, memory steady, app error rate near zero. The health check is `GET /healthz` with a 2s timeout, 2 consecutive failures to mark unhealthy, interval 5s. A deploy 90 minutes ago added a database connectivity probe to `/healthz`. Walk through triage and the fix.
What a strong answer looks like
Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.
0:00 of about 30 min
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.