Distributed Systems Troubleshooting Questions

Focused on diagnosing incidents specific to distributed architectures and multi service systems. Candidates should be able to detect and analyze network latency packet loss service to service communication failures cascading failures load balancing misconfiguration and data consistency anomalies. The topic covers observability practices such as distributed tracing aggregated metrics and logs correlation identifiers health checks and alerting; instrumentation strategies for cross service request flow mapping; and remediation patterns such as timeouts retries circuit breakers backpressure and resynchronization. Interviewers assess the ability to reason about partitioning and consistency models reproduce issues safely across services and propose mitigation and longer term fixes for distributed failure modes.

MediumTechnical

0 practiced

You suspect packet loss between two microservices in the same cluster causing TCP retransmits and increased response times. Which tcpdump or Wireshark filters and commands would you run to detect retransmissions and packet drops? What TCP fields and packet patterns indicate loss or duplicate ACKs? Provide example tcpdump commands you would use to capture relevant traffic.

HardTechnical

0 practiced

An event-driven pipeline occasionally processes events out-of-order, producing incorrect final state for entities. Propose designs to make processing idempotent and robust to reordering: sequence numbers, last-applied-version checks, vector clocks, or causal metadata. Also describe resynchronization strategies (snapshots, reconciliation jobs) to correct existing inconsistent state and trade-offs of each approach.

HardTechnical

0 practiced

Split-brain occurred: two replicas accepted writes and data diverged. Propose immediate containment actions to stop further divergence, a reconciliation plan for conflicting writes (automation vs manual resolution), and long-term architecture changes to avoid split-brain (quorum writes, fencing tokens, stronger leader election). Describe validation steps after reconciliation.

MediumTechnical

0 practiced

A Kafka consumer group's lag is steadily increasing for a topic. Describe a structured troubleshooting approach: which metrics (consumer throughput, processing time, rebalance frequency) and logs to inspect, how to determine whether producer, broker, or consumer is the bottleneck, and short- and long-term remediations (parallelism, partitioning, backpressure).

MediumTechnical

0 practiced

In a service mesh like Istio, mTLS between sidecars is failing for one service and producing 503s. Describe a step-by-step debug plan: how to check certificate issuance, mTLS policies, SNI mismatches, sidecar versions, and application behavior. Include commands or tools (kubectl, istioctl, openssl) and logs to inspect.

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