What is Cloud Spanner?
Answer
Cloud Spanner is Google's globally distributed, strongly consistent, horizontally scalable relational database. It is unique in combining ACID transactions with horizontal scaling across regions — a combination previously considered impossible (the "CAP theorem trade-off"). Key features: True horizontal scaling: add nodes to increase throughput without downtime. Global strong consistency: reads anywhere see the latest committed data. Standard SQL: ANSI SQL 2011 compatible. 99.999% SLA (five nines) for multi-region configurations. Automatic sharding: data is split (sharded) across nodes automatically. Use cases: financial systems, global inventory, games leaderboards — any application requiring a relational database that needs to scale beyond what a single instance can handle. It is significantly more expensive than Cloud SQL, justified only for global-scale workloads.