Cold start — init duration, heavy imports, VPC ENI delay
Dependencies — outbound network, IAM permissions, region mismatch
Minimal fix — smallest change; redeploy; verify with structured log line
Common failure modes
Symptom
Likely cause
Task timed out
Slow downstream, missing async, too much work in handler
Cannot find module
Bundle/packaging; wrong runtime
Access denied
IAM role, resource policy
Connection timeout
VPC/subnet/NAT; wrong security group
Works once then fails
State in /tmp; connection pool reuse
Practices
Structured JSON logs with requestId, stage, durationMs
Fail fast on missing required env with clear error message (no secret values)
Use X-Ray or vendor tracing for cross-service calls
Keep handlers thin; push heavy work to async queues when needed
Related skills
dynamic-config-management — env validation
observability-slo — alerts and SLOs for functions
gstack/investigate — general root-cause discipline
Clean-room workflow for serverless environments.
1---2name: serverless-debugging-23description: Serverless Debugging4---56# Serverless Debugging78Systematic debugging when traditional server logs and SSH are unavailable. Complements `test-failure-triage` with environment-specific constraints.910## When to use1112- Intermittent 5xx from functions13- Timeout or memory limit errors14- Works locally but fails when deployed1516## When not to use1718- Long-running container services with full shell access19- Client-only bugs (use browser DevTools skills)2021## Workflow22231. **Reproduce** — identify trigger (HTTP event, queue, schedule)242. **Logs** — cloud provider log group/stream; filter by request ID253. **Config** — compare env vars/secrets: local vs deployed (names only, never log values)264. **Limits** — timeout, memory, payload size, concurrency275. **Cold start** — init duration, heavy imports, VPC ENI delay286. **Dependencies** — outbound network, IAM permissions, region mismatch297. **Minimal fix** — smallest change; redeploy; verify with structured log line3031## Common failure modes3233| Symptom | Likely cause |34|---------|----------------|35| Task timed out | Slow downstream, missing async, too much work in handler |36| Cannot find module | Bundle/packaging; wrong runtime |37| Access denied | IAM role, resource policy |38| Connection timeout | VPC/subnet/NAT; wrong security group |39| Works once then fails | State in `/tmp`; connection pool reuse |4041## Practices4243- Structured JSON logs with `requestId`, `stage`, `durationMs`44- Fail fast on missing required env with clear error message (no secret values)45- Use X-Ray or vendor tracing for cross-service calls46- Keep handlers thin; push heavy work to async queues when needed4748## Related skills4950- `dynamic-config-management` — env validation51- `observability-slo` — alerts and SLOs for functions52- `gstack/investigate` — general root-cause discipline5354*Clean-room workflow for serverless environments.*
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Serverless Debugging It is listed under DevOps & Infra on SkillMD.
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charlieviettq (@charlieviettq) published this skill. Their other Agent Skills are listed on their SkillMD profile.
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