Building the future: highlights from Dropbox’s 2025 summer intern class

Here's a concise summary of the blog post in 2-3 sentences: Dropbox's immutable blob store, Magic Pocket, faced a significant increase in storage overhead due to increased fragmentation and under-filled storage volumes after a new service rollout. The existing compaction strategy couldn't effectively reclaim space from the long tail of severely under-filled volumes, highlighting a limitation in the steady-state approach. Dropbox developed a multi-strategy approach to drive overhead back down, combining compaction, garbage collection, and efficient redundancy to achieve better storage efficiency and control at exabyte scale.

Dropbox's server monorepo grew to 87GB, slowing down engineering velocity due to long clone times and approaching the 100GB GitHub limit. The team discovered that Git's delta compression was inefficiently storing internationalization files, causing rapid repository growth. A locally tested fix using an experimental flag reduced the repository size to 20GB, but further investigation showed that this solution was incompatible with GitHub's server-side optimizations.