SQL Server – Parallelism in a specific database is not active

I have a few databases with identical schemas, let's call them:



I have a query that takes 11 seconds to execute and returns 11,000 records in DB_A. However, if exactly the same query is executed in the same DB_B, it takes 40 seconds and returns 7,000 records.

The schema is identical, so the query is, but when I run it on DB_B, it goes to degree of parallelism 1, on DB_A it goes to 16.

I tried to set the threshold cost to 0 to enforce concurrency, but I got the same result.

Why is that? How can the same query that is executed in cloned databases behave so differently?

Any ideas are welcome.

I use SQL 2017 standard.