When we recently shipped  filesystem snapshots  in Vercel Sandbox to let teams capture and restore a sandbox's entire filesystem state, our initial engineering focus was entirely on reliability, making sure the system would never fail to snapshot or lose data. Once that foundation was stable, our attention turned to performance. p75 snapshot restores were taking over 40 seconds, and through parallelization and local caching, we brought that under one second. Link to heading What a snapshot looks like on disk Vercel Sandbox runs on the same infrastructure as our internal builds product, Hive . Each sandbox is an isolated container inside a Firecracker microVM. A snapshot is a compressed copy of the sandbox's disk.…