Amazon API Gateway Interview Questions and Answers

1. What is Amazon API Gateway?

   • Answer: Amazon API Gateway is a fully managed service that makes it easy for developers to create, publish, maintain, monitor, and secure APIs at any scale. It acts as a front door for applications to access back-end services, handling tasks like authentication, authorization, throttling, and monitoring.

2. What are the key features of API Gateway?

   • Answer: Key features include RESTful API creation, WebSocket support, request/response handling, authentication & authorization (using IAM, Cognito, etc.), throttling and quotas, monitoring and logging, integration with other AWS services (Lambda, EC2, etc.), API versioning, and deployment stages.

3. How does API Gateway handle authentication and authorization?

   • Answer: API Gateway offers several authentication methods including Amazon Cognito, IAM, custom authorizers (Lambda functions), and OAuth 2.0. Authorization is managed through IAM policies, resource policies, and custom authorizers, allowing fine-grained control over API access.

4. Explain the concept of API stages in API Gateway.

   • Answer: API stages represent different deployment versions of your API. You can have a development stage for testing, a staging stage for pre-production, and a production stage for live traffic. This allows for controlled rollouts and easy rollback to previous versions.

5. What are REST APIs and how are they created in API Gateway?

   • Answer: REST APIs are built around HTTP methods (GET, POST, PUT, DELETE, etc.) and resources. In API Gateway, you define resources (e.g., /users, /products) and associate HTTP methods with them, specifying integration requests (how the API interacts with backend services) and integration responses (how the API responds to clients).

6. How does API Gateway integrate with AWS Lambda?

   • Answer: API Gateway seamlessly integrates with AWS Lambda. When a request comes in, API Gateway can invoke a Lambda function to handle the request logic. The Lambda function processes the request and returns a response, which API Gateway then sends back to the client. This is a serverless architecture approach.

7. What are API Gateway request and response mappings?

   • Answer: Request mappings transform the incoming request from the client into a format suitable for the backend integration (e.g., converting JSON to XML). Response mappings transform the response from the backend integration into a format suitable for the client.

8. Explain the concept of throttling and quotas in API Gateway.

   • Answer: Throttling limits the rate of requests to your API, preventing overload. Quotas set limits on the total number of requests allowed within a given timeframe. Both are crucial for managing API performance and costs.

9. How does API Gateway handle errors and exceptions?

   • Answer: API Gateway can map HTTP status codes to custom error responses, providing customized error messages to clients. It can also be configured to handle exceptions from backend integrations and return appropriate error responses.

10. What are WebSocket APIs in API Gateway?

    • Answer: WebSocket APIs allow for real-time, bidirectional communication between clients and backend services. They're suitable for applications requiring real-time updates, such as chat applications or live dashboards.

11. How can you monitor the performance of your API Gateway?

    • Answer: API Gateway provides detailed monitoring through Amazon CloudWatch, offering metrics on request latency, error rates, throughput, and more. These metrics can be used to identify performance bottlenecks and optimize your API.

12. What are API Gateway custom authorizers?

    • Answer: Custom authorizers are Lambda functions that perform authorization checks beyond the built-in methods. They can implement complex authorization logic based on custom criteria, such as user roles, permissions, or data stored in a database.

13. How do you manage API keys in API Gateway?

    • Answer: API keys can be generated and managed in API Gateway. They provide an additional layer of security by requiring clients to provide a valid API key with each request. Usage plans can control the rate limits and quotas associated with specific API keys.

14. What are usage plans in API Gateway?

    • Answer: Usage plans define quotas and throttling limits for API keys. They allow you to control access to your API by limiting the number of requests from specific clients or groups of clients.

15. Explain the concept of caching in API Gateway.

    • Answer: API Gateway can cache responses from backend integrations, reducing latency and improving performance. Caching is configured on a per-stage basis and helps optimize response times, especially for frequently accessed data.

16. How can you deploy changes to your API Gateway?

    • Answer: Changes to your API are deployed to specific stages (e.g., dev, staging, prod). You can deploy changes using the AWS Management Console, the AWS CLI, or the API Gateway SDKs.

17. What are some best practices for designing APIs using API Gateway?

    • Answer: Best practices include using proper HTTP methods, designing intuitive resource paths, implementing robust error handling, using API keys and authorization, employing caching, monitoring performance, and versioning your APIs for backward compatibility.

18. How does API Gateway handle request transformation?

    • Answer: API Gateway uses mapping templates (Velocity Template Language) to transform requests and responses. This allows for modification of headers, path parameters, query parameters, and the request/response body.

19. What are the different types of integrations supported by API Gateway?

    • Answer: API Gateway supports various integration types, including Lambda function integrations, HTTP integrations (to other web services), AWS service integrations (e.g., DynamoDB, S3), and Mock integrations (for testing purposes).

20. How can you implement rate limiting with API Gateway?

    • Answer: Rate limiting is achieved through throttling settings in API Gateway. You can configure rate limits at the API level, stage level, or even using usage plans and API keys to control the request rate from specific clients.

21. What is the role of API Gateway in a serverless architecture?

    • Answer: In a serverless architecture, API Gateway serves as the entry point for all client requests, routing them to backend services (typically Lambda functions) without the need to manage servers. It handles all the infrastructure and scaling aspects.

22. How can you secure your API Gateway using IAM roles?

    • Answer: IAM roles are used to grant API Gateway access to other AWS services. For example, if your API interacts with S3, you'd create an IAM role with the necessary S3 permissions and associate it with the API Gateway integration.

23. What are some common security considerations when using API Gateway?

    • Answer: Security considerations include proper authentication and authorization, using API keys, implementing input validation, securing backend integrations, protecting against common attacks like DDoS, and regularly reviewing security best practices.

24. How can you deploy an API Gateway using infrastructure-as-code (IaC)?

    • Answer: You can use tools like AWS CloudFormation or AWS CDK to define your API Gateway infrastructure as code. This allows for automated deployments, version control, and repeatable deployments.

25. What are the different logging options available in API Gateway?

    • Answer: API Gateway integrates with CloudWatch to log API requests, responses, and errors. You can configure detailed logging to capture relevant information for debugging and monitoring.

26. How can you handle CORS (Cross-Origin Resource Sharing) with API Gateway?

    • Answer: API Gateway allows you to configure CORS settings to control which origins are allowed to access your API. This is crucial for enabling cross-origin requests from web applications.

27. What is the difference between a REST API and a WebSocket API in API Gateway?

    • Answer: REST APIs are request-response based, suitable for traditional HTTP interactions. WebSocket APIs enable persistent, bidirectional communication, ideal for real-time applications needing continuous data streaming.

28. How can you test your API Gateway endpoints?

    • Answer: You can test your API endpoints using the API Gateway console's built-in testing feature, using tools like Postman or curl, or by writing automated tests as part of your CI/CD pipeline.

29. Explain the concept of API Gateway request validators.

    • Answer: Request validators define rules to validate incoming requests. They check if the request body conforms to a specified JSON schema or if required query parameters are present. This improves the security and reliability of your API.

30. How can you implement authentication using Cognito with API Gateway?

    • Answer: Integrate Amazon Cognito User Pools as an authorizer. API Gateway will use Cognito to verify JWT tokens sent by clients, automatically authenticating requests.

31. What are the different pricing models for Amazon API Gateway?

    • Answer: API Gateway pricing is based on the number of requests, data transferred, and usage of features like custom authorizers and caching. There are different pricing tiers available to optimize costs.

32. How can you manage different versions of your API using API Gateway?

    • Answer: API Gateway supports API versioning through the use of different stages and base paths. You can create multiple stages for different API versions (e.g., v1, v2) to manage backward compatibility.

33. What are some common metrics to monitor in API Gateway CloudWatch?

    • Answer: Common metrics include Count, Integration Latency, Successful Integrations, Failed Integrations, Throttled Requests, and 4xx and 5xx error rates.

34. How can you use API Gateway with other AWS services like S3 or DynamoDB?

    • Answer: Use AWS service integrations within API Gateway to directly interact with services like S3 or DynamoDB. This simplifies the integration process and leverages the native capabilities of these services.

35. Explain the role of integration requests and responses in API Gateway.

    • Answer: Integration requests define how API Gateway sends requests to the backend. Integration responses define how API Gateway transforms and returns responses from the backend to the client.

36. What are mapping templates in API Gateway, and why are they important?

    • Answer: Mapping templates (using Velocity Template Language) enable transformations of requests and responses between API Gateway and the backend. They are crucial for data format conversion and request/response manipulation.

37. How can you handle binary data with API Gateway?

    • Answer: API Gateway supports binary data using specific content types (e.g., 'application/octet-stream'). Proper configuration of integration requests and responses is essential to handle binary data correctly.

38. What is the purpose of the `$context` variable in API Gateway mapping templates?

    • Answer: The `$context` variable provides access to various context information within the mapping template, including request details, stage variables, and API Gateway-specific data.

39. How can you set up a custom domain name for your API Gateway?

    • Answer: Configure a custom domain name using Amazon Route 53 and create a Base Path Mapping to associate it with your API Gateway.

40. How do you handle large payloads with API Gateway?

    • Answer: For large payloads, consider using binary media types and streaming responses. Configuring appropriate timeouts and limits is also crucial to prevent errors.

41. Explain the benefits of using API Gateway for microservices architecture.

    • Answer: API Gateway provides a central point of entry for microservices, simplifying routing, managing security, and applying cross-cutting concerns like rate limiting and monitoring across all services.

42. How can you troubleshoot common API Gateway issues?

    • Answer: Use CloudWatch logs and metrics to identify problems. Check integration logs, examine API Gateway configuration, and review your backend service for errors. Utilize the API Gateway console for debugging and testing.

43. What are some alternatives to Amazon API Gateway?

    • Answer: Alternatives include Kong, Apigee, and Azure API Management. The best choice depends on specific needs and integration with existing infrastructure.

44. How can you implement request validation using JSON Schema with API Gateway?

    • Answer: Define a JSON Schema that specifies the structure and data types of your request body. Configure API Gateway's request validator to use this schema and reject requests that don't conform.

45. Explain the concept of API Gateway's integration timeout.

    • Answer: The integration timeout sets a time limit for the backend integration to respond. If the backend doesn't respond within the timeout, API Gateway returns an error to the client.

46. How can you deploy API Gateway using AWS SAM (Serverless Application Model)?

    • Answer: Define your API Gateway and its integrations within a SAM template. AWS SAM simplifies the deployment of serverless applications, including API Gateway.

47. Describe how API Gateway interacts with other AWS services like DynamoDB.

    • Answer: API Gateway can use AWS service integrations to directly call DynamoDB. This means requests from API Gateway can perform DynamoDB operations (Get, Put, Update, etc.) without needing a separate Lambda function.

48. What are some best practices for designing API Gateway mapping templates?

    • Answer: Use clear variable names, modularize templates for reusability, test thoroughly, handle errors gracefully, and avoid unnecessary complexity.

49. How can you monitor the health of your API Gateway using CloudWatch alarms?

    • Answer: Create CloudWatch alarms based on key metrics (like error rate or latency) to receive notifications when performance degrades or errors exceed thresholds.

50. What are some strategies for handling API Gateway scaling?

    • Answer: API Gateway automatically scales to handle traffic; however, you might need to optimize backend services (like Lambda functions) to handle increased load. Consider using autoscaling for your backend resources.

51. How can you use API Gateway with VPC endpoints for improved security?

    • Answer: Configure VPC endpoints for your API Gateway to allow private communication between the API Gateway and resources within your VPC, reducing exposure to the public internet.

52. Explain how API Gateway can be used in a CI/CD pipeline.

    • Answer: Integrate API Gateway deployment into your CI/CD pipeline using tools like AWS CodePipeline. This enables automated deployments of API changes to different stages (dev, test, prod).

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