Clearbit utilizes Docker and CoreOS to efficiently manage over 70 internal services on an 18-machine EC2 cluster, handling more than 1.5 million API calls daily. CoreOS, a minimal operating system designed for Docker containers, integrates tools like etcd and fleet for distributed service management, providing an effective abstraction level without imposing strict architectural assumptions. Docker facilitates consistent application deployment across servers by packaging applications into standalone images. The deployment process at Clearbit starts with a git push, triggering a build server that creates and tags a Docker image, distributes it via fleet services, and updates the load balancer using etcd and HAProxy. The transition from old to new code is managed by a custom tool called "fluster," which promotes the new service and gracefully removes the old one. Future articles will explore deeper aspects of this infrastructure, including CoreOS setup and the open-sourcing of management tools like "fluster."