internal-aws-lambda

name	internal-aws-lambda
description	Use when /internal-aws selects the AWS Lambda lane for handlers, event sources, runtimes, packaging, retries, concurrency, cold starts, or Lambda-specific configuration.

Internal AWS Lambda

Own AWS Lambda handler, event-source, runtime, packaging, retry, concurrency, cold-start, and configuration behavior.

When to use

• Implementing or reviewing Lambda handlers in Python, Node.js, or TypeScript.
• Designing API Gateway, Function URL, or other HTTP-triggered request/response handling.
• Designing SQS-triggered batch processing, retry, DLQ, or partial-batch-failure flows.
• Packaging, dependency, cold-start, VPC, or runtime-configuration choices specific to Lambda.

Core guidance

• Keep the handler as a transport adapter; move business logic to testable helpers.
• Code to one event-source contract at a time: HTTP, queue, schedule, or async.
• Parse and validate inputs at the boundary; normalize data passed to business logic.
• Initialize AWS clients outside the handler when reuse is safe; keep imports small.
• Prefer modular SDK clients and narrow dependencies over broad convenience packages.
• Size timeout, memory, concurrency, batch size, and queue visibility timeout as one operating profile.
• Treat duplicate delivery, retries, and idempotency as normal for async triggers.
• Use environment variables for configuration; fetch secrets from managed secret stores.
• Log stable identifiers (request IDs, message IDs); do not log raw sensitive payloads by default.

Event-source guidance

• HTTP: normalize body, path, and query once; return transport-compatible JSON with explicit headers; keep CORS intentional.
• SQS: process records independently; handle poison messages explicitly; return only failed item identifiers when partial batch retry is enabled.
• Scheduled: make time-window assumptions explicit; guard against duplicate or overlapping execution.
• File-driven: avoid recursive triggers by separating input and output prefixes or buckets.

Load references/examples.md for minimal handler patterns and event-source checklists. Load references/sharp-edges.md when diagnosing cold starts, VPC latency, retry storms, response-shape mismatches, or file-ingest recursion. Load references/common-mistakes.md for the full mistake table.

Completion contract

• Unit tests run outside the Lambda runtime; AWS boundaries are mocked.
• HTTP handlers: malformed body, path, query, and error-response cases tested.
• Queue consumers: duplicate delivery, poison messages, timeout pressure, and partial batch failure tested.
• Code assumptions validated together with deployed timeout, memory, event-source, and queue configuration.
• Event contract, boundary normalization, retry behavior, and idempotency are explicit.