How would you debug production issues related to Consumer Groups and Rebalance?

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Quick interview answer

Debug Consumer Groups and Rebalance by confirming blast radius, checking lag/error metrics, grabbing profiles/traces, then mitigating before deep root-cause. Use Consumer Groups and Rebalance as the core idea. Example shape: 6 partitions, 3 consumers → each gets 2 partitions; add 4th consumer triggers rebalance..

Detailed answer

Production debug playbook for Consumer Groups and Rebalance: 1) Stabilize: rate-limit, shed load, or roll back if users are hurting. 2) Orient: dashboards for latency, errors, saturation tied to Consumer Groups and Rebalance. 3) Evidence: traces, profiles, logs with correlation IDs. 4) Hypothesize + prove with a safe experiment. 5) Fix + add a regression test/alert so it cannot silently return. Watch for: Long processing without pause; committing before side effects complete. Parent context: Use Consumer Groups and Rebalance as the core idea. Example shape: 6 partitions, 3 consumers → each gets 2 partitions; add 4th consumer triggers rebalance..

Full explanation

Interviewers score structured incident thinking: mitigate → measure → root cause → prevent. Each partition consumed by one consumer in group. Rebalance on member join/leave — can cause duplicate processing if offsets not committed carefully.

Follow-up questions

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Parent context — Consumer Groups and Rebalance

Use Consumer Groups and Rebalance as the core idea. Example shape: 6 partitions, 3 consumers → each gets 2 partitions; add 4th consumer triggers rebalance..

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