The development of Yugabyte SQL (YSQL), a distributed, highly resilient, PostgreSQL-compatible SQL API layer powered by DocDB, has been an engineering achievement that brings together two iconic database technologies. The YSQL architecture is designed to be scalable horizontally, with no single point of failure, and provides high resilience with native failover and repair capabilities. It also enables geo-distribution across multiple regions and supports cloud-native operations with zero downtime for schema changes or infrastructure migrations. Through a series of posts, the authors explain their design principles, tradeoffs, implementation details, and lessons learned, highlighting the benefits of YSQL as a PostgreSQL-compatible database that can complement existing investments in YugabyteDB.