This technical paper from Google describes Spanner, a globally distributed database that enables highly available and consistent data management across multiple datacenters. Spanner uniquely provides externally consistent distributed transactions, a feature that ensures a consistent view of data despite the challenges of distributed systems. This is achieved through a novel time API called TrueTime, which explicitly accounts for clock uncertainty, enabling Spanner to guarantee a globally consistent view of data across all its nodes. The paper explores the architecture, design choices, implementation details, and performance characteristics of Spanner, demonstrating its potential to handle massive datasets and complex operations across continents. The paper concludes by discussing future directions for Spanner, including further optimizations for performance and consistency, as well as the integration of more sophisticated database functionalities.