Top 20 AWS Lambda Interview Questions and Answers

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AWS Lambda is a serverless computing service by Amazon Web Services. It was launched in 2014 and was created by Tim Wagner to help developers run code without managing servers. With Lambda, you just write your function, and AWS runs it when needed. It is used in automation, real-time file processing, backend APIs, and more. Many roles like cloud developer, DevOps engineer, and backend engineer need Lambda skills. If you are applying for one of these jobs, the interview often starts with Lambda. So, let’s look at the most asked AWS Lambda interview questions and answers. 

Fun Fact: According to 6sense, over 34,296 companies around the world have started using AWS Lambda as a Platform-as-a-Service (PaaS) tool in 2025.

AWS Lambda Interview Questions for Freshers 

Here are some common AWS Lambda interview questions and answers to help freshers understand the basics and get ready for their first cloud job.

1. What is AWS Lambda and how does it work?

AWS Lambda is a serverless compute service. You write your code, upload it, and AWS runs it only when triggered. You don’t manage servers. Lambda automatically handles scaling and billing based on the number of requests.

2. Which programming languages are supported by AWS Lambda?

As of 2025, Lambda supports Python, Node.js, Java, C#, Go, Ruby, and PowerShell. You can also use custom runtimes or container images if needed.

3. What are the main components of an AWS Lambda function?

There are three:

• Event – the trigger data
• Handler – the function code that runs
• Context – metadata about the request and function environment

4. How do you create and deploy a simple Lambda function?

I open the AWS Lambda console, choose a blueprint or create a function from scratch, write or upload my code, set the permissions, and configure a trigger. Then I test it. For bigger projects, I use the AWS CLI or SAM.

5. What are the common triggers or event sources for AWS Lambda?

Common triggers include API Gateway, S3 (file uploads), DynamoDB Streams, SQS queues, CloudWatch events, and EventBridge.

6. What is the default execution timeout in AWS Lambda, and can it be changed?

The default timeout is 3 seconds. Yes, it can be changed. The maximum allowed timeout is 15 minutes (900 seconds).

Note: Interview questions on AWS Lambda often include basic concepts, real use cases, function limits, and how it integrates with other AWS services.

AWS Lambda Interview Questions for Experienced

Let’s go through some AWS Lambda interview questions and answers for experienced professionals.

7. How do you reduce cold starts in Lambda functions?

Use smaller deployment packages, pick faster runtimes like Node.js or Go, and enable provisioned concurrency for critical functions. You can also use SnapStart for Java-based Lambdas to preload the execution environment.

8. What are Lambda Layers, and how do you use them?

Lambda Layers are used to share code, libraries, or dependencies across multiple functions. Instead of bundling everything in each deployment, I put common code in a layer and attach it to my functions. It keeps things clean and saves time.

9. How do you monitor and debug AWS Lambda functions in production?

I use CloudWatch Logs for error output and CloudWatch Metrics to track invocations, duration, and errors. For deeper traces, I enable AWS X-Ray. I also set alarms for high error rates or long durations.

10. How do you manage configuration changes across multiple Lambda environments?

I use environment variables for most configs. For secrets or larger settings, I use AWS Systems Manager Parameter Store or Secrets Manager. I separate dev, staging, and prod configs clearly.

11. Can one Lambda function call another? What’s the best practice for doing this?

Yes, a Lambda can call another using the AWS SDK. I follow the principle of decoupling and often use SQS or Step Functions instead, especially when reliability or retries matter.

12. What are some real-world use cases where you used Lambda with other AWS services like SQS, Kinesis, or API Gateway?

I have used Lambda with API Gateway to build lightweight REST APIs. I have also used it with SQS for processing order queues and with Kinesis for streaming analytics in real time.

Also Read - Top 100+ AWS Interview Questions and Answers

AWS Lambda Scenario Based Interview Questions

These Lambda AWS interview questions are based on real scenarios to help you practice solving practical challenges you might face on the job.

13. How would you build a serverless REST API using Lambda and API Gateway?

I create a Lambda function that handles the logic. Then, I use API Gateway to set up routes like GET or POST and link them to the function. I choose Lambda Proxy integration so the full request is passed in. After deploying the API, I test using tools like Postman.

14. A Lambda function is intermittently timing out. How would you troubleshoot this?

First, I check CloudWatch Logs to see where the function is slowing down. I look at external calls, loops, or large payloads. I also check if timeouts are too short and increase them if needed. If the function interacts with other services, I test those latencies too.

15. How do you handle retries and failures when a Lambda processes messages from SQS?

I set a redrive policy with a dead-letter queue (DLQ). If a message fails after the max tries, it moves to the DLQ. I also use try-catch blocks in my code and log failed items clearly for later checks. 

16. How would you schedule a Lambda to run a cleanup task every night at midnight?

I create a rule in EventBridge with a cron expression for midnight. Then I set the Lambda as the target. The function runs on schedule without manual triggers.

Also Read - Top 50+ REST API Interview Questions and Answers

AWS Lambda Function Interview Questions

Here are some Lambda function in AWS interview questions to help you understand how Lambda functions work.

17. What happens in the lifecycle of a Lambda function execution?

The first time a Lambda runs, AWS creates a new container. This is called a cold start. It loads the code, sets up the runtime, and runs the handler. For following requests, the same container may be reused (a warm start) until it times out or is replaced.

18. What is the difference between context object and event object in a Lambda function?

The event object carries data from the trigger (like S3, API Gateway, or SQS). It contains inputs for the function. The context object gives metadata about the function’s environment – like the function name, timeout, memory, and request ID.

19. How do you package and deploy Lambda functions with external dependencies?

For Python, I create a folder, install dependencies with pip into it, zip the whole folder, and upload it. For Node.js, I use npm to install packages and zip the node_modules with the handler. I use the AWS CLI or SAM to deploy.

20. How do you securely access secrets or environment-specific values inside a Lambda function?

I use AWS Secrets Manager or Parameter Store. The Lambda gets an execution role with permission to fetch them. I avoid hardcoding. Sometimes I use encrypted environment variables, but not for sensitive data.

How to Prepare for AWS Lambda Interview?

AWS Lambda is widely used in cloud jobs across startups and large companies. So, here are some tips to help you prepare for interview: 

• Understand how Lambda works with other AWS services like S3, API Gateway and SQS
• Practice writing and deploying real Lambda functions
• Learn how to debug using CloudWatch and X-Ray
• Know how to reduce cold starts and handle timeouts
• Read common interview questions and practice speaking your answers out loud
• Use AWS free tier to test your code

Wrapping Up

With these 20 AWS Lambda interview questions and answers, you now have a solid base to prepare confidently. Practice the scenarios, understand how Lambda works, and stay updated with new features.

Ready to take the next step? Visit Hirist to find top AWS Lambda jobs, including roles that require AWS Lambda skills. Your next opportunity might be just a click away.

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