The why and how of this can be found here : https://github.com/Microsoft/BuildXL/blob/master/Documentation/Wiki/WhyBuildXL.md https://github.com/Microsoft/Buil

The why and how of this can be found here : https://github.com/Microsoft/BuildXL/blob/master/Documentation/Wiki/WhyBuildXL.md https://github.com/Microsoft/BuildXL/blob/master/Documentati... Seems what drove this was a 90 build times of 90 hours for and end to end build of Office. What I can gather this has a means of capturing all read/write operations for a build step and placing it in a cache store to determine if a change necessitates the rebuild of a component. Since it can hook in at a lower level, it isn't sensitive to time stamps for building. Actually quite interesting