Azure API Management Gateways, Products and Policies

Create an Azure API Management instance

Azure API Management (APIM) acts as a central proxy that sits between your client applications and your backend services. It is made up of three main components that work together to manage the lifecycle of your APIs. The API gateway handles all incoming traffic, routes requests to the correct backends, and verifies security credentials. The management plane is the control center where administrators configure APIs and view analytics, while the developer portal is a web portal where external developers can discover and learn how to use your APIs. When deploying APIM, you must choose a pricing tier, such as the Consumption tier for serverless environments or the Premium tier for enterprise networking and multi-region support.

Create and document APIs

To make your backend services public, you must define them inside your APIM instance. You can create APIs by importing existing definitions like an OpenAPI specification, or directly from Azure resources like a Function App or an App Service. APIM also supports API mocking, which allows you to simulate backend responses before the actual backend code is even written. This feature helps front-end and back-end teams work at the same time because the gateway can return sample data immediately without hitting a live database. You can also group multiple APIs into logical collections called products, which makes them easier to manage and secure as a single package.

Configure access to APIs

Securing your APIs is a critical step to ensure that only authorized clients can access your data. APIM uses subscriptions as the primary way to grant access to APIs and products. When a client requests access, they receive a unique subscription key that must be included in the header or query string of every incoming request. The gateway inspects this key at the boundary of your API environment and blocks any unauthorized requests before they can reach your backend. For higher security requirements, you can configure OAuth 2.0 or use client certificates to verify the identity of the client application during the secure connection handshake.

Implement policies for APIs

Policies are a powerful feature in APIM that let you change the behavior of your API through configuration rather than writing code. Policies are XML-based rules that run sequentially in four distinct phases: inbound processing, backend processing, outbound processing, and on-error handling. For example, an inbound policy can perform rate limiting to prevent too many requests from overwhelming your servers, or it can validate a security token. An outbound policy can modify the response headers or transform XML data into JSON format before it returns to the client. These policies can be applied globally to all APIs, to a specific product, to a single API, or down to a specific API operation.