Performance Debugging and Latency Investigation Questions
Finding the root cause of latency spikes: checking CPU/memory/disk/network utilization, profiling applications, querying slow logs, and identifying bottlenecks. Understanding the difference between resource exhaustion and an algorithmic problem. Using monitoring and tracing tools to narrow down where time is spent.
HardSystem Design
57 practiced
Design a retention and sampling policy for traces and metrics that allows SREs to debug latency spikes from the last 30 days, while keeping storage and egress costs within a fixed budget. Include tiered retention (hot/cold), sampling/sketching approaches, aggregation rollups, and how to keep high-fidelity data for critical windows.
HardTechnical
63 practiced
Implement an online change-point detection (e.g., CUSUM) in Python that ingests a stream of request latencies and raises an alert when a statistically significant upward shift in p99-level behavior occurs. Provide code and explain parameter choices (window size, thresholds) and how you avoid excessive false positives.
EasyTechnical
59 practiced
Explain the difference between latency and throughput from an SRE perspective. Give two concrete examples where increasing throughput does NOT reduce end-to-end latency for a user-facing API. Finally, list three specific metrics you would monitor to track both latency and throughput for a production HTTP service and explain why.
MediumTechnical
66 practiced
Write a PromQL query that computes the instant p99 request latency for job='frontend' over the last 5 minutes and returns a time series suitable for alerting when it exceeds 0.2s. Explain any assumptions about metric types and histogram naming conventions you used.
MediumTechnical
55 practiced
Write a Python script (or describe one precisely) to parse MySQL's slow query log and produce the top 10 query fingerprints by average latency over the last hour. Include how you would fingerprint similar queries that differ only by literals, and mention edge cases like multi-line queries and missing timestamps.
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