Database-related Slowdowns

When the server is slow, check if the problem is caused by database operations.
It is recommended to use database-specific tools.

You can also use the debug-sql server logging preset. Upon enabling, all the queries which take longer 1 second will be logged into the teamcity-sql.log file. The time can be changed by setting the teamcity.sqlLog.slowQuery.threshold internal property. The value should be set in milliseconds and is 1000 by default.

MySQL

Along with the server thread dump, please attach the output of the "show processlist;" SQL command executed in MySQL console. Like with thread dumps, it makes sense to execute the command several times if slowness occurred and send us the output.
Also, MySQL can be set up to keep a log of long queries executed with the changes in my.ini:

[mysqld]
...
log-slow-queries
long_query_time=15