API Management policies in Azure are powerful configuration statements that allow you to modify the behavior of APIs through sequential processing. These policies execute on the request or response of an API call, enabling you to transform, validate, and control API traffic effectively.
Policies a…API Management policies in Azure are powerful configuration statements that allow you to modify the behavior of APIs through sequential processing. These policies execute on the request or response of an API call, enabling you to transform, validate, and control API traffic effectively.
Policies are defined in XML format and organized into four sections: inbound (applied to incoming requests), backend (applied before forwarding to the backend service), outbound (applied to responses), and on-error (applied when exceptions occur).
Common policy implementations include:
**Authentication and Authorization**: You can enforce authentication using policies like validate-jwt to verify JSON Web Tokens, check-header to validate API keys, or authentication-certificate for client certificate validation.
**Rate Limiting and Throttling**: The rate-limit and rate-limit-by-key policies help protect your APIs from overuse by restricting the number of calls within a specified time period. Quota policies set limits over longer durations.
**Transformation**: Policies like set-header, set-body, and rewrite-uri allow modification of requests and responses. You can convert between JSON and XML formats, add or remove headers, and restructure payloads.
**Caching**: The cache-lookup and cache-store policies improve performance by storing responses and serving cached content for subsequent matching requests.
**Cross-Origin Resource Sharing (CORS)**: The cors policy configures browser-based access to your APIs from different domains.
**Validation**: Policies validate content against schemas, ensuring requests meet expected formats before reaching backend services.
Policies can be applied at different scopes: global (all APIs), product, API, or operation level. More specific scopes inherit from broader scopes, and you can use the base element to control inheritance behavior.
Policy expressions using C# syntax enable dynamic behavior based on context variables, request properties, and response data, making policies highly flexible for complex scenarios.
Implement Policies for APIs in API Management
Why It Is Important
API Management policies are essential for controlling API behavior, security, and performance. They allow you to transform requests and responses, enforce security measures, rate limit traffic, and implement caching. Understanding policies is crucial for the AZ-204 exam as they represent a core functionality of Azure API Management that developers must master to build enterprise-grade API solutions.
What Are API Management Policies?
Policies are a collection of XML statements that are executed sequentially on the request or response of an API. They act as a powerful mechanism to change the behavior of APIs through configuration rather than code. Policies can modify headers, transform payloads, validate content, and much more.
Policy Structure
Policies are organized into four sections:
• inbound - Executed when a request is received from a client • backend - Executed before the request is forwarded to the backend service • outbound - Executed before the response is sent to the client • on-error - Executed when an error occurs during processing
Policies are applied at different scopes in order of precedence:
1. Global scope - Applies to all APIs 2. Product scope - Applies to all APIs within a product 3. API scope - Applies to all operations within an API 4. Operation scope - Applies to a specific operation
Use the <base /> element to control where parent scope policies are executed relative to the current scope policies.
Policies support C# expressions using the @(expression) syntax. You can access context variables like: • context.Request - Access request properties • context.Response - Access response properties • context.User - Access subscription user information • context.Product - Access product information
Exam Tips: Answering Questions on Implement Policies for APIs in API Management
• Know the base element: The <base /> tag determines where inherited policies execute. Placing it at the top means parent policies run first.
• Distinguish rate-limit vs quota: rate-limit restricts calls per time window with a sliding window, while quota sets a fixed limit over a longer period
• Understand scope inheritance: Policies cascade from global to operation level. More specific scopes can override or extend parent policies.
• Watch for authentication scenarios: Know when to use validate-jwt for OAuth/OpenID Connect tokens vs authentication-certificate for client certificates
• Memorize common policy locations: Caching policies use cache-lookup in inbound and cache-store in outbound sections
• Practice XML syntax: Exam questions often test correct policy XML structure and attribute usage
• Know context variables: Questions may ask about accessing request/response data using context object expressions
• CORS handling: The cors policy belongs in the inbound section and handles preflight requests