Wikimedia Performance Team/Performance Review

The Wikimedia Performance Team provides a service critical to the sanity of Wikimedia production code and infrastructure in the form of Performance Reviews. The goal of these reviews is to ensure that major changes and deployments of new features do not result in performance regressions detrimental to the user experience.

Regressions in perceived performance can lead to user frustration and search engine ranking degradation, both likely to result in audience and traffic attrition. Performance reviews are a necessary step for all major changes deployed to Wikimedia production.

Timeline
Performance reviews for a given quarter must be requested at least 21 calendar days prior to the beginning of the quarter.

We are a small team and performance reviews are time-consuming, they are quarterly goals for us.

Once the quarter has started and the preparation steps have been performed by the requester (see below), we commit to completing the performance review within 30 calendar days.

Required preparation
Familiarise yourself with:
 * Wikimedia Performance Team/Page load performance
 * Wikimedia Performance Team/Backend performance

The main prerequisite to a performance review is to have the changes or features deployed to a Beta Cluster wiki.

If that isn't possible, the exception must be justified and the changes/feature will still have to be hosted on a wiki the performance team can access and SSH into (for example, in Wikimedia Cloud VPS). It's insufficient to merely point us to the code. Reviewing must involve zero setup for us. This differs from code review where pushing the code to Gerrit is enough preparation for the reviewer.

Beyond setup, it's also necessary for the requester to do a performance assessment of their own. Outlining potential performance bottlenecks, potential optimisations and including performance measurements. Web performance shouldn't be a concern completely offloaded to the Performance Team. New features and major changes should already have had their performance optimised to the best of the authors' abilities prior to being submitted to performance review.

How to request a performance review
Use the "Request Performance Review" form on Phabricator and enter the required information. Thank you!