How we delivered more performant and robust task lists in GitLab

This post details the technical implementation of performance and robustness improvements for GitLab task lists. It describes how the frontend was modified to send only the clicked task's text and line number to the backend, and how the backend verifies this specific task and updates the cached HTML directly using the `SOURCEPOS` flag of the CommonMark renderer and Nokogiri. This approach bypasses full markdown rendering, significantly increasing performance and preventing data overwrites during concurrent user interactions.