Vercel cut CDN metadata lookup P99 from 215.8 ms to 19.1 ms by sharding per-path files
Vercel Blog·medium signal
Vercel replaced one metadata object per path with roughly 200 KB JSONL shards that carry an embedded index and base64 byte offsets. The router binary-searches the shard and parses only the matching entry. P99 fell 91% (215.8 ms to 19.1 ms), the average fell 79% (8.59 ms to 1.81 ms), and deploys got 10 to 25% faster. The technique fits any system doing cold lookups against many small objects in blob storage.