Why it matters

Spanner uniquely combines scale + consistency + SQL. Understanding shapes global databases.

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The architecture

TrueTime: atomic clock + GPS for global clock bound.

External consistency: strongest consistency guarantee.

Spanner architectureMulti-region clusterglobalTrueTime clockbounded uncertaintyStrong consistencyexternalReads at consistent snapshot; writes commit globally strongly consistent
Spanner model.
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How it works end to end

Sharding: automatic by primary key.

PostgreSQL dialect: option for Postgres compat.

Cost: significantly higher than Cloud SQL.

Use case: global consistency + scale.