Optimizing Vercel Sandbox snapshots

Vercel reduced Sandbox filesystem snapshot restore latency from over 40 seconds to under 1 second through parallelized S3 downloads, multi-threaded decompression, and NVMe local caching. The optimization strategy uses HTTP range requests for parallel downloads, goroutine-based decompression, and stream piping to eliminate intermediate disk writes. Local caching achieves 95% hit rates, cutting p95 latency to under 10 seconds and enabling the new Automatic Persistence feature for instant sandbox resume cycles.