Reducing our monorepo size to improve developer velocity

This post explains how Dropbox reduced their server monorepo size from 87GB to 20GB (a 77% reduction), cutting clone times from over an hour to under 15 minutes.

• •The monorepo had grown to 87GB and was approaching GitHub's 100GB hard limit, with CI jobs paying the full clone cost repeatedly
• •Root cause was Git's delta compression heuristic, which uses only the last 16 characters of a file path to pair files — mismatching i18n files across languages instead of within them
• •An experimental --path-walk flag fixed the issue locally but was incompatible with GitHub's server-side optimizations like bitmaps and delta islands
• •The solution was a server-side repack using tuned --window and --depth parameters, which took ~9 hours but reduced the mirror from 84GB to 20GB
• •