Answer: By invoking an AWS Lambda function

**Explanation:** Amazon Lex chatbots use AWS Lambda functions to trigger backend processing when all required slot values are gathered and the chatbot is ready to execute an action. Here's why: 1. **AWS Lambda Integration**: Amazon Lex is designed to integrate seamlessly with AWS Lambda functions. When a chatbot needs to perform backend processing (like booking an appointment, processing an order, or validating data), Lex invokes a Lambda function. 2. **Fulfillment Process**: In Lex, this is called the "fulfillment" step. After all required slots are filled, Lex can either: - Return the slot values to the client application - Invoke a Lambda function for backend processing 3. **Why not the other options**: - **S3 (B)**: While S3 can store data, it doesn't trigger processing - it's a storage service - **SNS (C)**: SNS is for notifications, not for direct backend processing of chatbot actions - **EC2 (D)**: EC2 instances need to be running and managed, while Lambda provides serverless, on-demand execution 4. **Benefits of Lambda**: - Serverless (no infrastructure management) - Scales automatically - Pay-per-use pricing - Fast execution for chatbot responses This architecture allows Lex chatbots to perform complex backend operations without managing servers, making it ideal for chatbot implementations.

Author: Ritesh Yadav