After Web 8.5 broker database upgrade, CPU utilization continuously spiking to near 100% because of website load

- Customer has recently upgraded CM environment from Web 8.1.1 to Web 8.5.
- Customer is using the legacy publishing framework and in-process API.
- When the broker database was upgraded from Web 8.1.1 to Web 8.5, administrators see that the DB server CPU utilization is continuously spiking to near 100% as in below screenshot.  As a result, sites were not loading and publishing was unsuccessful.

- Before upgrade, average database connections were 25.  After database upgrade, connections are increasing from 25 to 100+.
- Publishing activity does not have a significant impact on the broker database CPU utilization, only site load.
- Hotfix CD_8.5.0_14124 has been applied to broker database, but issue persists.  This hotfix applies missing foreign key indexes on the broker database which would cause deadlocks on heavy load.  Also see KB article SDL Web 8.5 Deployer failing with java.nio.file.NoSuchFileException error due to missing indexes
- On inspecting the broker database, administrators see that the cd_broker generated queries do not have the NAMESPACE_ID as an included column.
 

Issue resolved after applying the in-process API hotfix CD_8.5.0.16977, which is a cumulative hotfix includes the original hotfix CD_8.5.0.16977.  As noted in below KB article, custom indexes should have the NAMESPACE_ID column.
In SDL Web, broker database server CPU goes to 100% gradually after browsing to a DD4T webpage and making taxonomy calls

See below KB article on instructions on how to download SDL Web hotfixes.
Where can I find hotfixes for SDL Tridion Sites/Web?