What are mutations in Google Spanner?

A mutation is a buffered write operation, either an insert, update, delete, or replace, applied to a Spanner table outside of SQL DML syntax, typically through a client library. Mutations are queued on a transaction object and only sent to Spanner when the transaction commits.

transaction.insert('Orders', ['CustomerId','OrderId','OrderDate'],
                    [1001, 5001, '2026-08-01']);

Mutations are often preferred over DML for simple, high-throughput writes because they skip SQL parsing and query planning, making them faster for straightforward row-level changes. DML remains useful when the write depends on a condition or needs to touch rows matched by a query.

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