API Gateway

Opening Scenario

You've written a Lambda function that handles HTTP requests. The function works — but Lambda can't receive raw HTTP connections. You need something between the internet and your Lambda (or your EC2/ECS backend) that accepts HTTP/HTTPS requests, routes them to the right backend, handles authentication, throttles abusive clients, and returns the response. What does that look like in AWS?

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Question Progression

Concept 1: What is API Gateway and what does it actually do?

Question Your Lambda handles business logic. Between the internet and Lambda, there's a gap — Lambda doesn't have a public IP or an HTTP server. What fills that gap and why does it matter what's there?

Reasoning An HTTP server does more than forward bytes — it terminates TLS, routes requests to handlers, enforces authentication, and handles protocol specifics. Running all of this yourself in code is possible, but it's operational work that doesn't differentiate your…