Serverless Event Stream Processing

This post defines serverless stream processing, stateless vs. stateful processing, FaaS, and serverless. It details how ksqlDB handles both stateless and stateful processing, and how AWS Lambda functions as a FaaS. A key contribution is the proposed pattern of combining ksqlDB with AWS Lambda for event-driven applications, where ksqlDB performs stateful stream processing and Lambda handles stateless tasks triggered by ksqlDB outputs. A concrete example is provided with a GitHub repository demonstrating a ksqlDB application integrated with AWS Lambda for two-way communication, processing stock trades and user data.