Tail latency triggers cascading timeouts
A request flows gateway → A → B → C. Each hop has a 3s client timeout. At 19:00, C develops a mild tail: most calls are fast but p99.9 hits 2.8s. You'd expect this to be harmless — 2.8s is under every 3s timeout. Instead, the gateway's error rate climbs to 8% and you see wasted work: C completes requests successfully that the gateway has already given up on, and B and A both retry. Dashboards: C's success rate is ~100% (it eventually answers), but its load is climbing; the gateway sees timeouts. No deploy on C; it's just a tail. How do you triage and mitigate?
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 40 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.