AWS Lambda Cleanup: When CloudWatch Metrics Lie
When you inherit a legacy AWS environment with dozens of Lambda functions and a mandate to clean up unused resources, the obvious first step is checking CloudWatch metrics. Invocation counts, error rates, duration stats - all there in neat graphs. But what happens when those metrics tell you a function has zero errors, yet it’s failing on every single execution? This week I investigated 45 Lambda functions to determine which could be safely deleted. What started as a simple metrics review turned into a forensic investigation revealing broken functions masked by misleading CloudWatch data, API Gateway routes pointing to deleted Lambdas, and scheduled jobs silently failing for months. ...