HOW WE MIGRATED THE DATABASE BEHIND EVERY VERCEL BUILD

Summary from the TLDR Data newsletter

Vercel migrated the state behind its build warm pool from Redis to DynamoDB because critical billing and container mappings needed durable storage, using dual writes, shadow reads, feature flags, and production comparisons to cut over safely. The migration exposed a hidden dependency on Redis's ultra-low latency, forcing Vercel to redesign an N+1-style supply loop around concurrency rather than serialized reads.