Optimizing Vercel Sandbox snapshots

What this post added

This post details performance optimizations for Vercel Sandbox's filesystem snapshot restore process. Key improvements include parallelizing S3 downloads using the `Range` HTTP header and AWS Go SDK's `transfermanager`, fanning out decompression across multiple goroutines, and streaming download data directly into decompression to eliminate intermediate file writes. A local NVMe disk cache using LRU eviction was implemented, caching decompressed images to achieve a 95% cache hit rate and reduce boot times to be bounded only by microVM and container startup.