Amazon API Gateway Interview Questions and Answers for 5 years experience

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 request routing.

2. Explain the different API Gateway deployment stages.

   • Answer: API Gateway allows deploying APIs to different stages like `dev`, `test`, `prod`, etc. This enables a controlled rollout process, allowing testing in different environments before releasing to production. Each stage is independent and points to different backend configurations.

3. How do you handle API authentication and authorization in API Gateway?

   • Answer: API Gateway offers various authentication methods like AWS IAM, Amazon Cognito, custom authorizers (using Lambda functions), OAuth 2.0, and API keys. Authorization is typically handled through custom authorizers which check user permissions based on the request context and configured policies.

4. Describe different API Gateway request mapping templates.

   • Answer: Mapping templates transform incoming requests and outgoing responses. They use Velocity Template Language (VTL) to manipulate request parameters, headers, and body. Common uses are transforming JSON to other formats, adding headers, or extracting specific data from the request.

5. How do you handle throttling and rate limiting in API Gateway?

   • Answer: API Gateway provides built-in throttling capabilities. You can configure rate limits at the API, stage, or method level to control the number of requests per second or minute. This prevents overloading backend systems and ensures availability.

6. Explain the concept of API Gateway caching.

   • Answer: API Gateway can cache responses from backend services, reducing latency and improving performance. This is particularly useful for responses that don't change frequently. You can configure caching at the method level, specifying cache keys and time-to-live (TTL).

7. How do you monitor and log API Gateway requests?

   • Answer: Amazon CloudWatch provides detailed metrics and logs for API Gateway. You can monitor metrics like request latency, error rates, and throughput. Logs contain information about individual requests, including timestamps, request parameters, and response codes.

8. What are API Gateway custom authorizers and how do you implement them?

   • Answer: Custom authorizers are Lambda functions that verify user identity and permissions. They receive the request context and return a policy indicating whether the request is authorized or not. Implementation involves creating a Lambda function, configuring it as a custom authorizer in API Gateway, and setting the authorization type to `AWS_IAM` or `CUSTOM`.

9. How do you handle different HTTP methods (GET, POST, PUT, DELETE) in API Gateway?

   • Answer: API Gateway supports all standard HTTP methods. You define resources and methods for each HTTP verb. Each method can have its own configuration, including request validators, integration requests, and response mapping templates.

10. Explain the concept of integration requests and responses in API Gateway.

    • Answer: Integration requests define how API Gateway interacts with backend services. They specify the integration type (HTTP, AWS service, Lambda function), the endpoint URL, and request mapping templates. Integration responses handle the response from the backend and map it to the API Gateway response.

11. How do you handle errors and exceptions in API Gateway?

    • Answer: API Gateway allows configuring error handling using error mapping templates and integration response configurations. This enables returning custom error responses based on HTTP status codes or exceptions from backend services, ensuring consistent error handling across your API.

12. Describe different ways to deploy an API Gateway API.

    • Answer: APIs can be deployed using the AWS Management Console, AWS CLI, or the AWS SDKs. The AWS CLI and SDKs offer automation capabilities, ideal for CI/CD pipelines. The console provides a visual interface for simpler deployments.

13. How do you use API Gateway with other AWS services?

    • Answer: API Gateway integrates seamlessly with various AWS services like Lambda, S3, DynamoDB, and ECS. It can be used as a central point of access for applications to interact with these services, simplifying architecture and management.

14. What are REST APIs and how do they differ from other API styles?

    • Answer: REST (Representational State Transfer) APIs are a common architectural style for building web services. They use standard HTTP methods (GET, POST, PUT, DELETE) and rely on resources identified by URLs. Other styles include SOAP, GraphQL, and gRPC, each with its own strengths and weaknesses.

15. Explain the concept of API Gateway request validation.

    • Answer: API Gateway allows validating incoming requests against defined schemas (JSON Schema, Swagger/OpenAPI). This ensures requests conform to the expected format, preventing invalid data from reaching backend services.

16. How do you handle CORS (Cross-Origin Resource Sharing) in API Gateway?

    • Answer: CORS allows web applications to access resources from different domains. API Gateway allows configuring CORS settings at the method level, specifying allowed origins, methods, and headers.

17. Describe different ways to manage API keys in API Gateway.

    • Answer: API keys can be generated and managed through the API Gateway console, CLI, or SDKs. They can be associated with specific users or applications, providing a way to control access and track usage.

18. How do you use API Gateway with serverless architectures?

    • Answer: API Gateway is a cornerstone of serverless architectures. It integrates tightly with Lambda functions, enabling event-driven architectures where API calls trigger Lambda functions to process requests.

19. Explain how to implement different types of API Gateway integrations (HTTP, AWS, Lambda).

    • Answer: HTTP integrations connect to external HTTP endpoints; AWS integrations connect to other AWS services directly; Lambda integrations invoke AWS Lambda functions. Each type requires specific configuration details in API Gateway.

20. How do you version your APIs in API Gateway?

    • Answer: API Gateway allows creating multiple versions of your API, allowing parallel operation of different versions. This enables a controlled migration process and ensures backward compatibility.

21. Describe how you would implement a CI/CD pipeline for deploying API Gateway APIs.

    • Answer: A CI/CD pipeline would involve using tools like AWS CodePipeline, CodeBuild, and CodeDeploy. Code changes are built, tested, and deployed to different stages (dev, test, prod) of API Gateway, automating the deployment process.

22. How do you handle request transformation and response transformation in API Gateway?

    • Answer: Request and response transformations are handled using mapping templates. These templates use VTL to modify the request before sending it to the backend and the response before it's returned to the client.

23. What are the best practices for designing and building secure APIs using API Gateway?

    • Answer: Best practices include using appropriate authentication and authorization mechanisms, validating all inputs, implementing robust error handling, enabling WAF (Web Application Firewall), using HTTPS, and regularly monitoring for security vulnerabilities.

24. Explain the role of API Gateway in a microservices architecture.

    • Answer: API Gateway serves as a central point of entry for accessing multiple microservices. It acts as a reverse proxy, routing requests to the appropriate microservice based on the request path or other criteria.

25. How would you troubleshoot a common API Gateway issue, such as a 500 error?

    • Answer: Troubleshooting a 500 error involves checking CloudWatch logs for detailed error messages, reviewing API Gateway integration logs, examining the backend service logs, and verifying the API Gateway configuration.

26. Describe your experience with using API Gateway's integration with Lambda functions.

    • Answer: [Describe specific experiences, e.g., handling asynchronous requests, using Lambda proxies, optimizing Lambda invocation, handling dead-letter queues, etc.]

27. How do you manage API Gateway access logs for auditing and security purposes?

    • Answer: Access logs are stored in CloudWatch Logs. They can be analyzed using CloudWatch Logs Insights or exported to other logging and analytics systems for auditing and security monitoring.

28. Explain your approach to designing a RESTful API.

    • Answer: [Describe an approach using principles like resource-based URLs, appropriate HTTP verbs, consistent data formats, versioning, etc.]

29. How have you used API Gateway to improve the performance and scalability of your applications?

    • Answer: [Describe specific examples, e.g., using caching, implementing throttling, optimizing mapping templates, employing appropriate integration types, etc.]

30. Describe your experience with using API Gateway's request and response validation features.

    • Answer: [Describe how you have used request validation schemas to ensure data integrity and prevent errors, including specific examples and the benefits achieved.]

31. How do you handle different authentication mechanisms in API Gateway? Give examples.

    • Answer: [Describe experiences with IAM, Cognito, API keys, OAuth 2.0, and custom authorizers, explaining how each mechanism was implemented and its use case.]

32. What are some common performance bottlenecks you've encountered with API Gateway and how did you resolve them?

    • Answer: [Describe specific examples of bottlenecks, such as slow backend integrations, inefficient mapping templates, or inadequate caching strategies, and how these issues were addressed.]

33. How do you use API Gateway's features to improve the developer experience?

    • Answer: [Describe experiences with features like Swagger/OpenAPI integration, API documentation, SDK generation, and the overall impact on developer productivity.]

34. What are some best practices for monitoring and alerting on API Gateway metrics?

    • Answer: [Describe best practices, including setting up appropriate CloudWatch alarms based on latency, error rates, and throughput, as well as using dashboards to visualize key metrics.]

35. Describe your experience with integrating API Gateway with other AWS services beyond Lambda.

    • Answer: [Describe specific examples of integrating with S3, DynamoDB, EC2, etc., highlighting the technical challenges and solutions implemented.]

36. How do you handle large datasets or complex business logic when using API Gateway?

    • Answer: [Describe approaches like offloading data processing to Lambda or other services, using asynchronous processing, and optimizing data structures for efficiency.]

37. How do you approach testing API Gateway APIs?

    • Answer: [Describe testing approaches using tools like Postman, AWS SDKs, automated testing frameworks, and unit/integration tests for backend services.]

38. What are the security implications of using API Gateway, and how do you mitigate them?

    • Answer: [Discuss security concerns such as unauthorized access, data breaches, and DDoS attacks, and the mitigation strategies employed, including IAM roles, WAF, and regular security audits.]

39. Describe your experience with migrating existing APIs to API Gateway.

    • Answer: [Describe the process, challenges, and lessons learned from migrating existing APIs, including considerations for backward compatibility and minimal disruption.]

40. How do you optimize API Gateway for cost efficiency?

    • Answer: [Describe cost-optimization strategies, such as using appropriate throttling limits, leveraging caching, and optimizing mapping templates to reduce processing time.]

41. How familiar are you with API Gateway's integration with OpenAPI/Swagger?

    • Answer: [Describe experience using OpenAPI/Swagger to define and document APIs, including importing and exporting specifications, and using tools to generate client SDKs.]

42. Describe a challenging API Gateway implementation you worked on and how you overcame the challenges.

    • Answer: [Describe a specific challenging project and detail the challenges encountered, the solutions implemented, and the results achieved.]

43. What are your preferred tools and technologies for working with API Gateway?

    • Answer: [List the tools and technologies used, such as the AWS Management Console, CLI, SDKs, Postman, Swagger/OpenAPI tools, and any other relevant tools.]

44. How do you stay up-to-date with the latest features and best practices for API Gateway?

    • Answer: [Describe methods used to stay updated, such as AWS documentation, blogs, AWS re:Invent sessions, online courses, and community forums.]

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