🚀 Serverless ECS Task Runner with Lambda Rate Limiting

WHY CUSTOM THROTTLING (and why NOT just API Gateway)?

When you expose your Lambda via a Public Function URL,
anyone with the link can launch containers and trigger your infrastructure.

To avoid surprise billing and uncontrolled usage,
this project demonstrates a custom throttling approach.

• Cooldown: Each unique URL can be processed only once every 3 minutes (1 request per 3 minutes).
• If you try more often, you'll receive a clear 429 Too Many Requests error.

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Why Not Just API Gateway Throttling?

• API Gateway offers built-in throttling, but
  Lambda Function URLs (PublicLink) do not have native throttling.
• For flexibility and demo purposes, I used Lambda PublicLink.
• Public endpoints need extra care to prevent abuse and unexpected costs.

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Why DynamoDB TTL (not just API Gateway, Redis, or S3)?

• DynamoDB TTL provides:
  • Flexible, per-resource or per-user limits (by URL, IP, or any parameter)
  • Scalable, cheap, fully serverless, with no cold starts
  • Easy to extend with custom logic: group quotas, rolling limits, advanced scenarios
• API Gateway throttling is the best option for traditional REST APIs,
  but here we wanted to try custom logic and more interesting scenarios.
• Note: If you just want a simple, robust rate limit for an API, use API Gateway.
  If you need more flexibility, DynamoDB is a strong serverless alternative.

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Lambda Concurrency: Extra Anti-Spam Protection

To further prevent spamming and accidental parallel execution,
Lambda concurrency is limited at the function level.
This ensures that even if multiple requests are made,
no more than X containers can run in parallel.

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🏃‍♂️ Live Demo

Try it yourself (rate limited: 1 request per 3 minutes per URL):

https://fhryedzhyvsq7wjuyg55sy4aki0ajrze.lambda-url.us-east-1.on.aws/?url=https://cursor.style

Or test with your own URL by replacing https://cursor.style:

https://fhryedzhyvsq7wjuyg55sy4aki0ajrze.lambda-url.us-east-1.on.aws/?url=YOUR_URL

Example:

• Google:
  https://fhryedzhyvsq7wjuyg55sy4aki0ajrze.lambda-url.us-east-1.on.aws/?url=https://google.com

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⚡️ How it works in real time

1. Open the demo link above (replace url= value to test any public web page).
2. Lambda function launches a container, parses the page, and returns the page title.
3. If you call the same URL again within 3 minutes, you'll get a 429 error ("Rate limit: try later").
4. Try different URLs or come back after the cooldown!

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🏗️ Solution Architecture

Flow steps:

1. User triggers Lambda via PublicLink (Function URL).
2. Lambda checks DynamoDB for a recent request (rate limiting by URL).
3. If within limit: Lambda records the request (TTL key).
4. Lambda launches ECS Task via ECR Docker image.
5. Lambda polls for ECS Task status; once finished, retrieves results from CloudWatch Logs.
6. Lambda returns the result (e.g., web page title) to the user.
7. If rate limit exceeded: returns 429 Too Many Requests.
8. Lambda concurrency setting prevents mass parallelization and limits potential abuse.

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📝 Takeaway

This project shows how you can combine multiple AWS managed services (Lambda, DynamoDB, ECS, ECR, CloudWatch)
to build a fully serverless, cost-controlled, public-facing backend.