HTTP API

HTTP API Overview

At its core, http api is about doing one thing well inside your AWS Lambda project. Once you understand the pattern, you can apply it consistently across features and teams.

Good http api pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

export const handler = async (event) => {
  const { httpMethod, pathParameters, queryStringParameters } = event;
  const id = pathParameters?.id;

  if (httpMethod === 'GET') {
    return respond(200, { id, message: 'ok' });
  }

  return respond(405, { message: 'Method not allowed' });
};

function respond(statusCode, body) {
  return {
    statusCode,
    headers: { 'content-type': 'application/json' },
    body: JSON.stringify(body),
  };
}

This handler reads request details from the API Gateway event and returns a proxy-integration response.

HTTP API Example

// handler.mjs
export const handler = async (event, context) => {
  // 1. read input from the event
  // 2. do the work
  // 3. return a response (or throw on error)
};

• Start from a minimal HTTP API example and grow it only as needed.
• Keep configuration explicit so HTTP API behaves the same in every environment.
• Name things clearly so teammates understand your HTTP API at a glance.
• Add tests around HTTP API early to lock in expected behaviour.

AWS Lambda Cheatsheet

Handy reference for working with http api in AWS Lambda and Node.js.

How HTTP API Works in AWS Lambda

HTTP API runs inside the managed Lambda execution environment. AWS provisions a micro-VM, loads your Node.js code, runs any module-scope initialisation once, and then invokes your handler for each event.

This handler reads request details from the API Gateway event and returns a proxy-integration response.

• Handlers should be small and do one job well.
• Initialise SDK clients and config outside the handler to reuse them on warm starts.
• Return quickly and let event sources handle retries where possible.
• Emit structured logs so CloudWatch and X-Ray can correlate activity.

Practical Guidance for HTTP API

On real projects, http api works best when it is observable, secure, and cheap to run. Grant least-privilege IAM, validate every input, and keep the deployment package small.

Common Mistakes

• Skipping error handling and edge cases when wiring up http api.
• Leaving http api untested, so regressions slip into production.
• Over-engineering http api before you actually need the extra flexibility.
• Ignoring documentation, which makes http api hard for the next developer to change.

Key Takeaways

• HTTP API is a core part of working effectively with AWS Lambda.
• Start small and keep http api focused on a single responsibility.
• Apply consistent patterns so http api scales across your project.
• Test and document http api to keep it maintainable over time.