MySQL 5.x

Currently running slow query logging to catch anything taking longer than 10 seconds. Not much is showing up, but we are still seeing performance issues and are concerned that our problems may be caused by a flood of relatively fast queries.
If we drop this threshold down from 10 seconds to 5, could this itself impact performance? What if we dropped it down to 1, or zero?

Logging will definitly come at some cost.

But if you are not shure about the number of querys, you could first check the status information where every query is counted.

You can use "MySql Administrater" which gives you the details in graphs which allow to easily observe usage peaks.


Andreas

I'm sure you've covered these things but are you sure it's not a locking issue? Has anything changed recently? Would it be worth mentioning what storage engine you use and whether you use replication.