AWS Lambda Interview Questions and Answers for 2 years experience

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AWS Lambda Interview Questions & Answers

  1. What is AWS Lambda?

    • Answer: AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. You upload your code, and Lambda takes care of everything required to run and scale it, from the underlying compute infrastructure to code execution and scaling.

  2. Explain the core components of an AWS Lambda function.

    • Answer: A Lambda function consists of code (written in supported languages like Node.js, Python, Java, etc.), a handler function (the entry point for your code), an execution role (defining permissions), and configuration settings (memory, timeout, etc.).

  3. What are the different ways to trigger an AWS Lambda function?

    • Answer: Lambda functions can be triggered by various events, including S3 uploads, API Gateway requests, DynamoDB streams, CloudWatch events (scheduled events or custom events), SNS messages, Kinesis streams, and more.

  4. How does AWS Lambda handle concurrency and scaling?

    • Answer: Lambda automatically scales based on incoming requests. It spins up multiple instances of your function to handle concurrent invocations. You can configure concurrency limits at the function and account level for better control.

  5. Explain the concept of Lambda layers.

    • Answer: Lambda layers allow you to package reusable code, libraries, or dependencies and share them across multiple Lambda functions. This helps in reducing code duplication and improving maintainability.

  6. What is an execution role in AWS Lambda and why is it important?

    • Answer: The execution role defines the permissions your Lambda function has access to. It dictates which AWS services your function can interact with (e.g., S3, DynamoDB). Without a proper role, your function won't be able to access necessary resources.

  7. What are environment variables in AWS Lambda and how are they used?

    • Answer: Environment variables provide a way to configure your Lambda function without modifying the code. They are key-value pairs that can store sensitive information (like database credentials) or configuration parameters.

  8. How do you handle errors and exceptions in AWS Lambda functions?

    • Answer: You can handle exceptions using standard error handling mechanisms in your chosen programming language (try-catch blocks). Lambda also provides CloudWatch logs to track errors and monitor function execution.

  9. Explain the concept of dead-letter queues (DLQs) in Lambda.

    • Answer: DLQs are used to capture failed invocations of your Lambda function. When a function invocation fails, the event can be sent to a designated SQS queue or SNS topic for later processing or analysis.

  10. How can you monitor the performance of your Lambda functions?

    • Answer: CloudWatch provides metrics and logs for monitoring Lambda function performance. You can track invocation duration, errors, throttles, concurrency, and more. CloudWatch dashboards can visualize this data.

  11. What are Lambda function versions and aliases?

    • Answer: Versions are immutable snapshots of your function code. Aliases are pointers to specific versions, allowing you to easily switch between different versions in production without affecting the underlying code.

  12. Explain the difference between synchronous and asynchronous invocations of Lambda functions.

    • Answer: Synchronous invocations wait for the function to complete before returning a response. Asynchronous invocations send the request and return immediately; the function runs in the background.

  13. How can you optimize the performance of your Lambda functions?

    • Answer: Optimization techniques include choosing the right memory allocation, minimizing code size, using efficient algorithms, leveraging Lambda layers, and optimizing database interactions.

  14. Describe your experience with Lambda function deployments.

    • Answer: [Describe your experience with deployment methods like AWS CLI, SAM, CloudFormation, etc. Mention any challenges faced and how you overcame them.]

  15. How do you handle dependencies in your Lambda functions?

    • Answer: [Describe your approach to managing dependencies using package managers like npm, pip, Maven, etc., and utilizing Lambda layers for shared dependencies.]

  16. What are some security best practices for AWS Lambda functions?

    • Answer: Use least privilege principle for IAM roles, encrypt sensitive data, regularly review and update dependencies, use VPCs for network security, and implement proper logging and monitoring.

  17. How do you handle large payloads in Lambda functions?

    • Answer: For large payloads, use S3 for storage and pass the S3 object key as an event to your Lambda function. Process the data in chunks to avoid exceeding memory limits.

  18. What are some common challenges you have faced while working with AWS Lambda?

    • Answer: [Describe real-world challenges, such as cold starts, debugging issues, managing concurrency, dealing with large datasets, etc., and explain your solutions.]

  19. Explain your experience with serverless frameworks like Serverless Framework or AWS SAM.

    • Answer: [Describe your experience using any serverless framework, highlighting benefits like improved deployment, testing, and management.]

  20. How do you troubleshoot Lambda function failures?

    • Answer: Utilize CloudWatch logs, X-Ray tracing, and debugging tools to identify the root cause of failures. Analyze error messages and logs for clues.

  21. What is the difference between Lambda@Edge and regular Lambda functions?

    • Answer: Lambda@Edge runs at the edge locations of CloudFront, closer to end-users, for faster content delivery and improved latency. Regular Lambda functions run in AWS regions.

  22. How do you handle state management in Lambda functions?

    • Answer: Use external services like DynamoDB, Redis, or other databases to manage state since Lambda functions are stateless. Avoid storing state within the function itself.

  23. What are the different pricing models for AWS Lambda?

    • Answer: Lambda is priced based on the number of requests and the execution duration of your functions. It also considers memory allocation.

  24. How do you integrate Lambda with other AWS services?

    • Answer: Lambda integrates seamlessly with many AWS services through triggers and APIs. Examples include S3, DynamoDB, API Gateway, SNS, SQS, Kinesis, and more.

  25. Explain your understanding of Lambda's cold starts.

    • Answer: Cold starts occur when the first invocation of a Lambda function takes longer due to the initialization of the execution environment. Strategies to mitigate cold starts include provisioning concurrency and using a warming service.

  26. How do you test your Lambda functions?

    • Answer: Use unit tests within the code, integration tests that mimic real-world events, and end-to-end tests using tools like SAM or similar frameworks.

  27. What are some best practices for writing efficient Lambda functions?

    • Answer: Use appropriate data structures, optimize algorithms, minimize I/O operations, handle exceptions gracefully, and utilize Lambda layers for dependencies.

  28. Explain your experience with deploying Lambda functions to different AWS regions.

    • Answer: [Describe your experience with deploying to multiple regions, considering factors like latency, cost, and data locality.]

  29. How do you manage secrets and sensitive information in your Lambda functions?

    • Answer: Use AWS Secrets Manager to securely store and retrieve sensitive data, avoiding hardcoding credentials in your code.

  30. Discuss your experience with using Lambda for event-driven architectures.

    • Answer: [Discuss specific examples of building event-driven systems with Lambda, including event sources and how you handled event processing.

  31. How do you handle different concurrency levels in your Lambda functions?

    • Answer: Use reserved concurrency to guarantee a minimum number of available instances, and monitor concurrency metrics in CloudWatch to adjust configurations based on load.

  32. What are some strategies for reducing Lambda function costs?

    • Answer: Optimize memory allocation, reduce execution time, use reserved concurrency strategically, and leverage spot instances where appropriate.

  33. Explain your familiarity with AWS Lambda Powertools.

    • Answer: [Describe your experience with any Lambda Powertools, outlining the advantages of using these libraries for common tasks like logging, tracing, and metrics.]

  34. How do you ensure high availability for your Lambda functions?

    • Answer: Deploy to multiple Availability Zones, use asynchronous invocations to handle failures gracefully, implement proper retry mechanisms, and monitor closely for potential issues.

  35. Describe your experience using Lambda for batch processing.

    • Answer: [Discuss your experience with using Lambda for large-scale batch jobs, including strategies for handling large datasets and managing processing time.

  36. What are the limitations of AWS Lambda?

    • Answer: Limitations include execution time limits, memory constraints, cold starts, and the potential for vendor lock-in.

  37. How do you debug Lambda functions locally?

    • Answer: Use SAM CLI or similar tools to emulate the Lambda environment locally, allowing for easier debugging before deployment.

  38. Describe a complex Lambda function you have built and the challenges you faced.

    • Answer: [Describe a complex project, highlighting the architecture, technologies used, challenges encountered, and the solutions implemented.]

  39. How do you ensure your Lambda functions are idempotent?

    • Answer: Design functions to handle repeated invocations with the same input without producing different or unintended results. This often involves using unique identifiers and checking for existing state before processing.

  40. What are your preferred methods for testing Lambda integrations with other services?

    • Answer: Use mocking frameworks to simulate external service responses during unit testing. For integration tests, use real services and check for proper interaction and data flow.

  41. How do you handle scaling challenges in Lambda when dealing with unpredictable traffic spikes?

    • Answer: Monitor CloudWatch metrics closely to identify scaling needs. Adjust concurrency limits as required. Use techniques like queuing to handle spikes gracefully and avoid throttling.

  42. How familiar are you with using VPCs with Lambda functions?

    • Answer: [Explain your experience with configuring Lambda functions within VPCs to access resources on private subnets, including considerations like security groups and network configuration.]

  43. What are your thoughts on using Lambda for long-running tasks?

    • Answer: Lambda is not ideal for long-running tasks due to timeout limits. For such tasks, consider using EC2, ECS, or EKS.

  44. How do you version control your Lambda function code?

    • Answer: Use Git or a similar version control system to track changes to the function code and manage different versions effectively.

  45. Explain your experience with implementing CI/CD pipelines for AWS Lambda functions.

    • Answer: [Discuss your experience using tools like Jenkins, GitLab CI, AWS CodePipeline, etc., for automating the build, test, and deployment process.]

  46. Describe your experience with troubleshooting Lambda function performance issues related to memory allocation.

    • Answer: [Discuss how you identified and resolved performance issues related to insufficient or excessive memory allocation, referencing specific examples if possible.]

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