A developer built an SMS microservice using Python, Twilio, and Redis Pub/Sub to send alert messages without overloading the core service. The project consists of a subscriber that listens for incoming messages on a Redis channel and sends SMS using Twilio, and a publisher that sends messages to the same channel. The services can be run independently and communicate through Redis Pub/Sub, allowing for scalability and flexibility. The developer provides a step-by-step guide to setting up the environment, building the subscriber and publisher applications, and testing the communication between them.