Kristian Köhntopp

Senior Scalability Engineer at Booking.com.

Latest Blog Posts

MySQL: Tracing a single query with PERFORMANCE_SCHEMA

My task is to collect performance data about a single query, using PERFORMANCE_SCHEMA (P_S for short) in MySQL, to ship it elsewhere for integration with other data....

fork, exec, wait and exit

This is the english version of a 2007 article. In de.comp.os.unix.linux.misc somebody asked:...

Embracing the Stream

So this happened: CentOS Project shifts focus to CentOS Stream...

Earlier Activities

Not JOINing on PERFORMANCE_SCHEMA

The tables in PERFORMANCE_SCHEMA (P_S) are not actually tables. You should not think of them as tables, even if your SQL works on them. You should not JOIN them, and you should not GROUP or ORDER BY t...

On the Observability of Outliers

At work, I am in an ongoing discussion with a number of people on the Observability of Outliers. It started with the age-old question “How do I find slow queries in my application?” aka “What would I ...