Vitess

Vitess is a database clustering system for horizontal scaling of MySQL, originally developed at YouTube in 2010 to solve the challenges of running thousands of MySQL instances serving billions of queries per day. It was open-sourced in 2012, joined the Cloud Native Computing Foundation (CNCF) in 2018, and graduated from the CNCF in 2019, becoming only the second project after Kubernetes to achieve graduated status. Vitess combines the ACID guarantees and SQL compatibility of MySQL with the horizontal scalability of NoSQL databases, enabling applications to scale from a single MySQL instance to a cluster of hundreds of shards without changing application code. Key features include: transparent sharding (automatically distributing data across multiple MySQL instances based on a configurable sharding key, with support for range-based, hash-based, and custom sharding strategies), resharding without downtime (dynamically splitting or merging shards while the system continues to serve traffic, using VReplication for row-level change data capture and replication), connection pooling (the vtgate proxy multiplexes client connections over a pool of MySQL connections, similar to PgBouncer for PostgreSQL), query routing and rewriting (vtgate parses incoming SQL queries, determines which shards contain the requested data, routes the queries to the appropriate shards, and aggregates results), cross-shard transactions (using two-phase commit for ACID transactions that span multiple shards), schema management (applying schema changes across all shards atomically), a VSchema (Vitess Schema) layer that abstracts the physical shard layout from the application, backup and restore management, and a comprehensive management API (via vtctld) for cluster administration. Vitess powers databases at YouTube, Slack, Square, Pinterest, and GitHub. As of 2026, Vitess has over 12,000 stars.