Scenario-based Interview Questions on APIM (Azure API Management)

Here are some APIM Interview Questions scenario-based and tricky with their probable solutions or answers:

Scenario-Based Questions

Migrating Existing APIs

Approach for Migration Process:

• Identify existing APIs and their endpoints: This could involve documenting all existing APIs, their functionalities, and endpoints.
• Create corresponding API definitions in Azure API Management: Import existing API definitions (e.g., OpenAPI, Swagger) or manually define endpoints in Azure API Management.
• Configure authentication, policies, and transformations: Ensure that authentication mechanisms, policies, and data transformations are mirrored in Azure API Management.
• Test each API in the new environment: Verify functionality and compatibility by testing requests and responses against the new Azure API Management environment.

Handling Varying Authentication Methods

Handling Different Authentication Mechanisms:

• Use Azure API Management policies, such as set-header or authentication, to accommodate various methods.
• For example, to support OAuth 2.0, configure OAuth authentication in Azure API Management and apply policies to enforce client credentials or token-based authentication.

Mitigating High Traffic Performance Issues

Strategies for Performance Improvement:

• Implement caching policies: Use cache-lookup and cache-store policies to cache responses and reduce backend calls.
• Utilize rate-limiting policies: Apply quota-by-key or rate-limit-by-key policies to control incoming traffic based on client keys or subscription IDs.
• Scale horizontally: Add more Azure API Management instances or leverage auto-scaling to distribute the load effectively.

Transforming XML Requests to JSON Responses

Transforming Requests and Responses:

• Use policies like set-body and set-header: Example policy to transform XML to JSON:

  <inbound>
      <base />
      <choose>
          <when condition="@(context.Request.Headers.GetValueOrDefault("Content-Type") == "application/xml")">
              <set-header name="Content-Type" exists-action="override">
                  <value>application/json</value>
              </set-header>
              <set-body>@{
                  var xml = context.Request.Body.As<string>(preserveContent: true);
                  var jsonObject = JsonConvert.SerializeXNode(XDocument.Parse(xml));
                  return jsonObject;
              }</set-body>
          </when>
      </choose>
  </inbound>

Preventing Data Exposure and Rectification

Preventing Data Exposure and Rectification:

• Implement robust security policies: Use policies like rewrite-uri or validate-jwt to enforce authentication and authorization.
• Rectification steps: Immediately identify and rectify exposed data, adjust API policies, and enforce stricter access controls. Communicate changes to affected parties and review access permissions thoroughly.

Tricky Questions

Enforcing Different Rate Limits Based on User Roles or Subscriptions

Solution:

• Use policy expressions to evaluate user roles or subscription tiers: Example policy using choose and when statements to enforce different rate limits:

  <rate-limit-by-key calls="1000" renewal-period="60" counter-key="@(context.Subscription.Id)" />
  <choose>
      <when condition="@(context.User.IsInRole("Premium"))">
          <set-backend-service backend-id="premiumBackend" />
      </when>
      <otherwise>
          <set-backend-service backend-id="basicBackend" />
      </otherwise>
  </choose>

Handling API Versioning for Backward Compatibility

Solution:

• Utilize versioning strategies: Example using URL-based versioning:

  /api/v1/resource
  /api/v2/resource

Or using custom headers:

  Accept-Version: v1
  Accept-Version: v2

Policies can be used to route requests to the appropriate version based on the URL or header.

Guarding Against Potential DDoS Attacks

Solution:

• Implement Azure DDoS Protection Standard: Activate DDoS Protection Standard for the Azure API Management service to mitigate network layer attacks.
• Use rate-limiting policies: Apply rate-limiting policies to control the number of requests per client or IP address.
• Employ API management policies: Utilize policies to monitor and block suspicious traffic patterns or implement IP-based filtering to block malicious IPs.

Customizing Error Responses Based on API Operations

Solution:

• Customize error responses using policies: Example policy to return a custom error response:

  <choose>
      <when condition="@(context.Response.StatusCode == 404)">
          <return-response>
              <set-status code="404" reason="Not Found" />
              <set-body>Custom 404 Error Message</set-body>
          </return-response>
      </when>
  </choose>

Minimizing Disruption During Backend Updates

Solution:

• Staged deployments: Utilize deployment slots in Azure API Management to deploy updated backend services gradually. Redirect traffic to the updated version while keeping the older version available for consumers.
• Canary releases: Route a small percentage of traffic to the updated backend to validate changes before a full rollout.

APIM Interview Questions: See Also

• BizTalk Interview Questions
• Azure Interview Questions