What is AWS Lambda?
Why Interviewers Ask This
Interviewers use this question to quickly assess whether a candidate has the foundational knowledge required for Serverless Architecture development. It reveals whether you understand the building blocks that more complex concepts rely on.
Answer
AWS Lambda is Amazon's serverless compute service and the most widely used FaaS platform. It runs code in response to events and automatically manages the underlying compute resources. Key characteristics: (1) Supported runtimes — Node.js, Python, Java, Go, Ruby, C#/.NET, and custom runtimes via Lambda Layers; (2) Triggers — API Gateway, S3, DynamoDB Streams, SQS, SNS, EventBridge, Cognito, and 200+ other services; (3) Execution limits — up to 15 minutes, 10GB memory, 512MB ephemeral disk (/tmp), 6MB payload limit; (4) Concurrency — up to 1000 concurrent executions by default (soft limit, can be raised); (5) Billing — charged per 1ms of execution time and per million requests. Lambda functions are stateless — any state must be stored in external services (DynamoDB, S3, ElastiCache).
Common Mistake
A common mistake is memorizing definitions without understanding implications. When asked this question, go one level deeper — explain what happens when this concept is misused or ignored.