l;dr: I made Patchwork a lot faster by looking at what database queries were being generated and optimizing them either by making Django produce better queries or by adding better indexes.

Introduction to Patchwork

One of the key bits of infrastructure a bunch of maintainers of Open Source Software use is a tool called Patchwork. We use it for a bunch of OpenPOWER firmware development, several Linux subsystems use it as well as freedesktop.org.