OpenTelemetry + CloudWatch Logs Insights: Tracing Serverless Apps

Correlating OpenTelemetry traces with CloudWatch Logs Insights across Lambda and Step Functions is a common senior interview scenario — here's exactly how to answer it.

You'll learn:

• How to propagate trace context (W3C TraceContext headers) across Lambda invocations and Step Functions state transitions so trace IDs land in your structured logs
• Configuring the AWS Distro for OpenTelemetry (ADOT) Lambda layer to auto-instrument functions without cold-start penalties
• Writing CloudWatch Logs Insights queries that join on trace_id to reconstruct an end-to-end execution timeline across services
• Where correlation breaks — async Step Functions callbacks, missing X-Amzn-Trace-Id propagation, and log sampling mismatches
• Trade-offs between ADOT, X-Ray native SDK, and a third-party collector like the OpenTelemetry Collector on Fargate

Keywords: OpenTelemetry Lambda tracing, CloudWatch Logs Insights trace correlation, ADOT Step Functions, serverless observability interview questions

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