MongoDB has introduced External Functions in its Atlas Stream Processing, enabling direct invocation of AWS Lambda from streaming pipelines to enrich, validate, and transform data in real-time. This feature, available through the $externalFunction pipeline stage, integrates external logic services like AWS Lambda, allowing users to leverage existing business logic and perform AI/ML inference without embedding the logic within the pipeline itself. AWS Lambda, a scalable serverless compute service, can be used synchronously or asynchronously within the pipeline depending on whether an immediate response is required. A practical application of this is demonstrated through a solar energy company that uses synchronous external functions to monitor real-time telemetry from solar devices, enriching data with status updates and diagnostics before storing it in MongoDB Atlas. This capability enhances stream processing by making data processing smarter and more adaptable, with potential use cases in various fields like fraud detection and personalization.