Mastering AWS Lambda: Key Interview Topics and Preparation Tips

AWS Lambda is a cornerstone of serverless architecture, enabling developers to run code without managing servers. Whether you’re preparing for an interview or looking to deepen your understanding, this guide covers essential Lambda topics, key use cases, and advanced concepts to showcase your expertise.

What is AWS Lambda?

Standard Answer:
AWS Lambda is a compute service that lets you run code without provisioning or managing servers.

Advanced Answer:
AWS Lambda offers:

• No server management: Abstracts infrastructure concerns.

• Automatic scaling: Handles variable workloads seamlessly.

• High availability: Runs across multiple Availability Zones.

• Pay-as-you-go: Charges only for execution time.

Use Cases:

• API backends.

• Event-driven automation.

• Alexa Skills.

• ETL jobs.

Related AWS Serverless Services

AWS Lambda integrates with other serverless services to build scalable applications.
Criteria for a service to be serverless:

• No servers to manage.

• Automatic scaling.

• High availability.

• Pay-as-you-go pricing.

Examples:

• Compute: AWS Lambda.

• Storage: Amazon S3, DynamoDB.

• Integration: API Gateway, SQS, EventBridge, Step Functions.

• Analytics: Amazon Athena, QuickSight.

Handling Lambda Cold Starts

What are cold starts?
Cold starts occur when AWS initializes a new container for a Lambda function, causing latency during the first invocation.

Mitigation Techniques:

• Provisioned Concurrency: Pre-warm containers for critical workloads.

• Code Optimization:

  • Use lightweight libraries.

  • Minimize dependencies.

• Global Initialization: Reuse persistent connections outside the handler.

• Smaller Deployment Packages: Optimize code for faster initialization.

Using Custom Container Images

Can you use your own container image with Lambda?
Yes, AWS Lambda supports custom container images.

Benefits:

• Run custom runtimes or specialized libraries.

• Reuse existing containerized workloads.

Key Consideration: Modify the container slightly to integrate with Lambda’s requirements.

Scaling: Lambda vs. Fargate

AWS Lambda:

• Automatically scales by creating new instances per request.

• Integrates with AWS services like S3 and EventBridge.

• Execution limit: 15 minutes.

AWS Fargate:

• Scales by launching additional pods.

• Handles multiple concurrent connections.

• Persistent container runtime, even during inactivity.

Allocating CPU in Lambda

AWS Lambda does not allow direct CPU allocation. Instead:

• Memory increase automatically increases CPU.

• Use context.get_remaining_time_in_millis() to monitor runtime limits.

Securing AWS Lambda Functions

Best Practices:

• IAM Roles: Limit resource access per function.

• Resource Policies: Restrict who can invoke functions.

• Environment Variable Encryption: Use AWS Secrets Manager or KMS.

• Network Security: Use VPC to control traffic.

EventBridge vs. SQS

EventBridge:

• Advanced routing and filtering of events.

• Supports third-party SaaS integrations.

SQS:

• Simple message queuing.

• Reliable and cost-effective.

Decision: Use EventBridge for complex event patterns; use SQS for simple workflows.

Serverless vs. Kubernetes

When to use Serverless:

• Event-driven workloads.

• Focus on business logic without managing infrastructure.

When to use Kubernetes:

• Long-running applications.

• Workloads requiring container orchestration and control.

Hybrid Approach: Combine API Gateway with EKS/ECS as a backend.

Challenges in Serverless Architecture

• Cold Start Latency: Mitigate with provisioned concurrency.

• Monitoring and Debugging: Use AWS X-Ray and CloudWatch.

• Scaling Limits: Know account-level limits.

• Cost Management: Avoid redundant invocations.

Interview Tips

• Focus on real-world examples: Share challenges and solutions.

• Highlight trade-offs: For example, EventBridge vs. SQS.

• Understand cost implications: Optimize memory and concurrency settings.

• Demonstrate architectural knowledge: Explain event-driven and API-first patterns.

Conclusion

AWS Lambda is a versatile and powerful service for building serverless applications. By mastering these key topics and understanding real-world use cases, you can excel in interviews and advance your career in cloud computing. Ready to dive deeper? Start building projects using Lambda and explore how it integrates with other AWS services.