Vitess is an open-source database clustering system for MySQL designed to increase resilience, scalability, and performance by running multiple instances of MySQL on one or more servers, using a lightweight proxy to route queries intelligently, and automatically detecting when an instance goes offline. It enables horizontal sharding with minimal application changes, balancing the load across multiple servers, and improves performance through efficient connection management, allowing thousands of clients to be handled simultaneously without overloading individual MySQL processes. PlanetScale leverages Vitess to power its databases, providing a scalable and performant database platform that increases developer velocity while eliminating the need for managing underlying infrastructure.