Stale leader processing after GC pause
Your job scheduler uses a lock in ZooKeeper to elect a single 'leader' worker that processes a queue. At 11:50 you see duplicate side effects: some jobs run twice (double-charged invoices). Dashboards: a worker (worker-7) had a 12s JVM GC pause at 11:48; during that pause ZooKeeper expired its session and a new leader (worker-3) was elected and started processing; then worker-7 resumed and kept processing jobs as if it were still leader for ~9s before noticing. The DB has no fencing on writes. 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 45 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.