Harness CI's architecture is built to manage up to a million builds per day, utilizing microservices, Kubernetes, and asynchronous processing to ensure reliability and resilience, even under surge loads. The system's design principles emphasize simplicity, extensibility, scalability, and high reliability, allowing users across teams to create and execute pipelines efficiently. The platform's microservices are hosted on a GCP Kubernetes cluster, enabling automatic scaling to accommodate fluctuating demand, while ensuring seamless execution through asynchronous message queues and event-driven architecture. Harness CI also implements a sophisticated webhook processing system and pipeline execution framework to handle high volumes of traffic and ensure consistent performance. The use of fully managed solutions like MongoDB and Redis, alongside auto-scaling capabilities, minimizes operational overhead and prevents system bottlenecks. The architecture includes comprehensive disaster recovery plans and monitoring tools to maintain high availability and system health, allowing Harness CI to provide a robust and user-friendly experience.