Something’s Up with Parallelism in Azure SQL DB Serverless


Or perhaps another way to phrase that is, Microsoft is up to something with parallelism. I don’t know how long it’s been this way – could even be since the launch of Azure SQL DB Serverless – but I just now noticed it while helping a client with a slow query.

When you view an actual execution plan for a parallel query in SQL Server 2022 & prior, and in regular Azure SQL DB, you can right-click on an operator to see how the work is broken up across threads:

This is useful when you’re troubleshooting problems with unbalanced