AWS Lambda is the most widely used serverless compute service. When you need to run code without managing servers, handle variable workloads, or build event-driven architectures, Lambda is often the go-to solution.

But knowing when to use Lambda, how it scales, and understanding its limitations is what separates good answers from great ones. Many candidates propose Lambda without understanding cold starts, concurrency limits, or when it becomes more expensive than containers.

This chapter covers the practical knowledge you need for interviews: execution model, scaling behavior, cold starts, event sources, pricing trade-offs, and how Lambda compares to alternatives like ECS and Kubernetes.

Whether you are designing an image processing pipeline, a webhook handler, or a real-time data processor, understanding Lambda will help you make better architectural decisions.

1. When to Choose Lambda