Cloud Spanner
A globally distributed, strongly consistent relational database offering both SQL semantics and horizontal scalability beyond what a single Cloud SQL instance can provide. It is the right choice specifically when a workload needs both relational query capability and massive scale simultaneously, not simply because a workload feels large or important.
Frequently Asked Questions
What specific problem does Cloud Spanner solve that a sharded Cloud SQL setup can't?
Manually sharding a relational database across regions breaks cross-shard transactions and joins — you lose ACID guarantees the moment data spans shards. Spanner solves this using TrueTime, Google's globally synchronized clock infrastructure, to provide external consistency across globally distributed nodes without sacrificing SQL semantics or transactional integrity. It's essentially the only managed database offering both horizontal scale and strict relational consistency simultaneously, at a real infrastructure and cost premium.
What's the most common mistake teams make when adopting Spanner?
Choosing it because the workload 'feels important' rather than because it's actually outgrown a single-node relational database — Spanner's pricing and operational complexity aren't justified for moderate-scale workloads that Cloud SQL handles fine. Another common issue is poor primary key design: sequential keys (like auto-incrementing IDs) create hotspots since Spanner distributes data by key range, so keys need to be designed for even distribution across splits.