Optimizing Vercel Sandbox snapshots
By Steven Van ·
Parallel downloads and multi-threaded decompression cut Vercel Sandbox snapshot restores from over 40 seconds to under one.
Restoring a Vercel Sandbox from a snapshot now takes under a second, down from a p75 of over 40 seconds. The speedup comes from two changes to the restore path: snapshot downloads from S3 are now split into parallel range requests instead of one sequential download, and decompression of the custom VHS format now runs across multiple goroutines instead of one frame at a time.
- Parallel S3 range downloads, tuned for concurrency and chunk size, made downloads 2-5x faster.
- Feeding decompression to multiple goroutines instead of a single thread made the VHS-to-image restore 2-4x faster, depending on snapshot size.
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