What is Amazon API Gateway? A plain-English explainer
Amazon API Gateway is a managed service for creating, publishing, securing and managing APIs, supporting REST, HTTP and WebSocket interfaces at scale — in effect, a front door that sits in front of your backend services and handles the concerns every API needs before a request ever reaches your application code. Building an API is not just about writing the code that answers a request; it also means authenticating callers, protecting the backend from being overwhelmed, and routing each request to the right place, and doing all of that yourself, consistently, across every endpoint adds up quickly. API Gateway centralises that work into one managed layer in front of whatever is actually doing the processing. Here is what a gateway solves, how it commonly pairs with AWS Lambda, and when you would reach for it.
What an API is, briefly
Our what-is-an-api and what-is-a-rest-api explainers cover the underlying concepts properly. In short, an API is a defined way for one piece of software to request something from another, and a REST API is a common style of API built around standard web requests. API Gateway is not itself the API logic — it is the managed layer that fronts whatever is actually answering those requests.
What API Gateway actually does
API Gateway gives you a single, managed entry point for your API: it accepts incoming requests, authenticates and authorises callers, throttles traffic to protect whatever is behind it, and routes each request to the correct backend — which might be a Lambda function, another AWS service, or an HTTP endpoint elsewhere. It also handles the operational concerns around that traffic, such as logging and monitoring requests, without you building any of that by hand.
Because this layer is centralised, every endpoint behind the gateway gets the same authentication, throttling and monitoring applied consistently, rather than each backend service having to implement its own version of the same concerns.
The problems it solves
Without a gateway, each backend service ends up handling its own authentication, rate limiting and request validation, which is both repetitive and easy to get inconsistent across a growing set of services. API Gateway moves that work to one place in front of everything, so backend services can focus purely on their own logic.
It also insulates backends from traffic spikes and misuse: throttling and request limits at the gateway protect whatever is behind it from being overwhelmed, rather than every individual service needing to defend itself.
API Gateway with Lambda: a common pattern
A frequent combination is API Gateway in front of AWS Lambda functions — our what-is-aws-lambda explainer covers Lambda itself. The gateway handles the API-facing concerns (routing, authentication, throttling), while Lambda runs the actual request-handling code without any servers to manage on either side. This pairing is a standard way to build a fully serverless API on AWS, with no infrastructure provisioned for either the front door or the logic behind it.
When you would use API Gateway
API Gateway fits whenever you are exposing an API to callers — internal services, mobile or web clients, or external partners — and want authentication, throttling and routing handled centrally rather than rebuilt inside every backend. It is less necessary for purely internal calls that never cross a genuine API boundary, where the overhead of a managed front door adds little.
Pricing model, and where API Gateway appears in certification study
API Gateway is billed on a consumption basis — pay for the API calls it handles, with no gateway infrastructure to provision yourself. Exact rates change over time, so treat that as the model and check AWS’s own pricing page for current figures.
API Gateway is a core topic in the AWS Developer Associate exam, particularly alongside Lambda in serverless application design, and it appears in the Solutions Architect Associate exam as part of building decoupled, API-driven architectures. As with the other services covered here, this article stays introductory — the detail of configuring routes, authorisers and stages is exam-depth material our /revision study library is built to cover.
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