How can Node.js applications be monitored and what tools would you use?
Instruction: Describe approaches and tools for monitoring Node.js applications.
Context: This question assesses the candidate's familiarity with monitoring and performance analysis tools and practices in the context of Node.js applications.
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Start with user-visible service objectives: successful requests, latency distributions and availability for important operations. Monitor traffic and errors together so a quiet or failing endpoint does not look healthy merely because its average latency is low.
Collect Node-specific signals such as event-loop delay/utilization, CPU, heap/RSS, garbage collection and active resource pressure. Also monitor connection pools, queue age, database/provider latency and worker restarts. Rising memory is a symptom to investigate, not automatic proof of a leak...