Top AWS Lambda Interview Questions You Must Prepare For in 2025

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AWS Lambda has become one of the most widely used serverless computing services in the cloud. If you’re preparing for an AWS interview, understanding AWS Lambda in detail can help you stand out. This blog covers the top AWS Lambda interview questions and their answers to ensure you are fully prepared.

  1. What is AWS Lambda?

AWS Lambda is a serverless compute service provided by Amazon Web Services (AWS). It allows you to run code without managing or provisioning servers. Lambda automatically scales based on incoming events and charges you only for the compute time consumed.

Key Points to Mention:

  • Serverless, fully managed compute service
  • Event-driven architecture
  • Cost-effective (pay-as-you-go)
  • Supports multiple programming languages (Python, Node.js, Java, Go, etc.)
  1. What is a Lambda Function in AWS?

A Lambda function is the code or logic you write that gets executed when triggered by an event. Each function runs in its own isolated execution environment, and AWS Lambda manages the infrastructure needed to run the code.

Key Points to Mention:

  • It consists of handler functions written in supported programming languages.
  • Lambda functions are stateless and ephemeral.
  • AWS takes care of resource management, scaling, and execution.
  1. How to Create a Lambda Function in AWS?

Here is a step-by-step process for creating a Lambda function in AWS:

  • Log in to the AWS Management Console.
  • Navigate to AWS Lambda in the Services menu.
  • Click on Create Function.
  • Choose one of the options:
  • Author from scratch (create a function manually).
  • Use a blueprint (pre-built function templates).
  • Provide the function name, runtime (e.g., Python, Node.js), and execution role.
  • Write your code in the inline editor or upload it as a .zip file.
  • Configure triggers like S3, DynamoDB, or API Gateway.
  • Save and deploy the function.
  • Test the Lambda function using test events.
  1. Lambda is a Service Offered by AWS. Explain Its Key Features.

AWS Lambda is a core service provided by Amazon Web Services for serverless application development. Its key features include:

  • Serverless Execution: No need to manage infrastructure or servers.
  • Event-Driven: Lambda executes in response to events from other AWS services (S3, DynamoDB, etc.).
  • Automatic Scaling: Scales automatically based on incoming requests or events.
  • Cost-Effective: Charges are based on actual compute time (millisecond-level billing).
  • Multi-Language Support: Python, Node.js, Java, Go, Ruby, .NET, etc.
  • High Availability: AWS ensures fault tolerance and reliability.
  1. What is AWS Lambda Used For?

AWS Lambda is used to build scalable, event-driven, and serverless applications without the need to manage servers. It is widely adopted for various use cases such as:

  • File Processing: Real-time image, video, or file processing in Amazon S3.
  • Data Transformation: Stream data from Kinesis, DynamoDB, or IoT devices.
  • API Backends: Lambda integrates with Amazon API Gateway to serve backend APIs.
  • Automating Workflows: Automate tasks with AWS Step Functions or SNS triggers.
  • Database Events: Perform operations in response to changes in Amazon DynamoDB or Aurora.
  • Scheduled Tasks: Run cron-like jobs using AWS EventBridge or CloudWatch Events.
  1. How Does AWS Lambda Work?

AWS Lambda works in the following manner:

  • Trigger Event: An event triggers the Lambda function, such as an S3 upload, DynamoDB update, or API request.
  • Execution Environment: Lambda launches a secure environment to execute the function.
  • Execution: Your code processes the input event and returns a response.
  • Automatic Scaling: Lambda handles scaling based on the number of incoming events.
  • Resource Cleanup: The execution environment is terminated once the process completes.
  1. What Are the Advantages of AWS Lambda?

AWS Lambda offers several benefits over traditional server-based architectures:

  • No Server Management: AWS handles infrastructure and resource provisioning.
  • Cost-Efficiency: Pay only for the execution time.
  • Automatic Scaling: Lambda scales automatically with workload demands.
  • Quick Deployment: Deploy functions in minutes.
  • Event-Driven: Integrates seamlessly with AWS services for event-based triggers.
  1. What Are AWS Lambda Layers?

Lambda Layers allow you to manage code libraries, dependencies, and runtime components separately from your function code.

Key Points to Mention:

  • Up to 5 layers can be attached to a function.
  • Layers reduce deployment package size and improve code reusability.
  • Useful for shared libraries or SDKs.
  1. What Is the Maximum Timeout for AWS Lambda?

The maximum execution timeout for AWS Lambda is 15 minutes. If a function exceeds this limit, the execution is terminated, and the invocation will fail.

  1. How to Handle Cold Starts in AWS Lambda?

Cold starts occur when Lambda initializes a new execution environment. To mitigate cold starts:

  • Use provisioned concurrency to keep the function warm.
  • Optimize your code and reduce dependencies.
  • Use smaller, efficient runtimes.
  • Schedule regular invocations using CloudWatch Events.

Ready to Dive Deeper into AWS Lambda?

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