Q: How do you design observability for serverless functions such as AWS Lambda where instances are short-lived and you cannot scrape them like normal servers?

Serverless observability must use the platform telemetry path because functions may start and disappear before a pull-based scraper can reach them.

• Logs: Structured logs to CloudWatch Logs or a collector subscription.
• Metrics: Invocation count, errors, duration, throttles, concurrency, iterator age for streams, and DLQ depth for async failures.
• Custom metrics: Business outcomes such as orders processed or payment failures.
• Traces: Enable distributed tracing and propagate trace context through API Gateway, queues, and downstream calls.

I would capture: For serverless, absence of hosts does not mean absence of operations. You move observability to invocations, events, and managed-service metrics.

• Cold starts: Track initialization time separately from handler duration.
• Timeouts and retries: Alert on retry storms, partial batch failures, and poison messages.