I'm building an app with serverless functions and need performance monitoring

For serverless apps, performance monitoring should focus on the metrics that actually affect user experience and cost:

What to monitor

• Latency
  • p50 / p95 / p99 execution time
  • end-to-end request latency, not just function runtime
• Cold starts
  • frequency and added delay
• Errors
  • function failures, timeout rates, retries
• Throughput
  • invocations per minute, concurrency
• Resource usage
  • memory consumption, CPU if available, duration billed
• Dependencies
  • database, cache, third-party API latency and failures
• Cost signals
  • invocation count, duration, storage, egress

Recommended approach

1. Instrument every function

Add structured logs and tracing:

• request ID / correlation ID
• function name
• duration
• status code / error type
• upstream dependency timings

2. Use distributed tracing

This is especially important in serverless because one user request may span: API Gateway → Function A → Queue → Function B → DB

Use:

• OpenTelemetry
• a managed APM tool if you want faster setup

3. Capture cold starts explicitly

Track:

• isColdStart=true/false
• initialization time
• memory size and runtime version

4. Send metrics to a time-series backend

Examples:

• CloudWatch / AWS X-Ray
• Datadog
• New Relic
• Grafana Cloud
• Honeycomb
• Prometheus + Grafana for custom setups

Good dashboards

Build dashboards for:

• function latency percentiles
• error rate by function/version
• cold start rate over time
• dependency latency
• timeout count
• invocation volume
• cost per 1k requests

Alerts to set

• error rate above threshold
• p95 latency above threshold
• timeout spikes
• cold start rate increase after deployment
• dependency failures
• sudden cost jumps

Practical tips

• Keep logs structured and consistent
• Sample traces if volume is high
• Tag metrics by environment, version, and region
• Measure after deploys to catch regressions
• Watch memory sizing: too low increases duration, too high increases cost

If you want a simple stack

A common setup is:

• OpenTelemetry for instrumentation
• Cloud provider logs/metrics for basics
• Grafana/Datadog/New Relic for dashboards and alerts

If you tell me your cloud provider and runtime, I can recommend a concrete setup and library stack.