Under the hood
Database engine
Constant Time Recovery: how Azure SQL stopped undoing work row by row
Microsoft explains Constant Time Recovery, the design that stopped Azure SQL recovery time from scaling with the amount of work an interrupted transaction had done. A persistent version store plus logical revert let the engine mark an aborted transaction and clean up lazily instead of walking the log row by row. The work ships as Accelerated Database Recovery: always on in Azure SQL Database, opt-in on SQL Server.