Final answer:
AWS Lambda functions must be stateless because they are designed to run in an event-driven, serverless computing environment. Stateless functions offer benefits for scalability, availability, and fault tolerance. Although stateless, Lambda functions can utilize external services or databases to store and retrieve persistent data.
Step-by-step explanation:
AWS Lambda functions must be stateless because they are designed to run in an event-driven, serverless computing environment. Stateless means that the function does not rely on any external state or data that persists between invocations. Each time a Lambda function is invoked, it starts fresh with no knowledge of previous invocations.
Statelessness offers several benefits for scalability, availability, and fault tolerance. It allows Lambda functions to be easily scaled horizontally, meaning multiple instances of the function can be launched to handle a high volume of requests. If a function fails or crashes, another instance can be automatically spawned to take its place, ensuring high availability. Additionally, statelessness simplifies the deployment and management of Lambda functions, as there is no need to manage or synchronize shared state across multiple instances.
Although Lambda functions are stateless, they can still utilize external services or databases to store and retrieve persistent data between invocations. For example, a function can store data in an Amazon S3 bucket or query a database like Amazon DynamoDB.