6.1.1.2. Implementing an APIM Instance and Policies

1. Create an APIM Instance:

• In the Azure Portal, search for "API Management" and select "Create".
• Fill in subscription, resource group, region, organization, and admin email.
• Choose a pricing tier (Developer is suitable for testing, Basic/Standard/Premium for production with higher SLAs).
• Review and create. Provisioning may take 20–30 minutes.

2. Import and Publish APIs:

• In your APIM instance, go to "APIs" > "+ Add API".
• Select import method: OpenAPI/Swagger, Azure Function, or App Service (for backend).
• Provide the API definition (e.g., OpenAPI JSON) or backend link.
• Configure display name, URL suffix, and product (product groups APIs for consumers).
• Save and publish. The API is now accessible via the APIM gateway.

3. Apply Policies: APIM policies are configuration-driven statements that modify API behavior.

• Rate Limiting/Throttling: Add a rate-limit policy to restrict request rates (e.g., 100 calls/min). This protects your backend services from overload.
• Authentication/Authorization: Use validate-jwt for JWT (JSON Web Token) tokens or require client certificates.
• Caching: Apply cache-lookup and cache-store to cache responses and improve performance.

⚠️ Common Pitfall: Exposing backend services directly to the internet alongside APIM. This bypasses all the security and governance policies enforced by the APIM gateway.

Key Trade-Offs:

• Performance vs. Security/Transformation: Each policy adds a small amount of latency to the request pipeline. While negligible in most cases, highly complex policies can impact performance.

Practical Implementation: APIM Rate Limit Policy (XML)

<policies>
    <inbound>
        <base />
        <!-- Limit calls to 5 per 15 seconds per subscription key -->
        <rate-limit calls="5" renewal-period="15" />
    </inbound>
    <backend>
        <base />
    </backend>
    <outbound>
        <base />
    </outbound>
    <on-error>
        <base />
    </on-error>
</policies>

Reflection Question: How does implementing Azure API Management (APIM), by providing a centralized gateway with features like security policies, traffic management, and transformation capabilities, fundamentally enable organizations to publish, secure, transform, and monitor APIs across any environment?