Book: TypeScript in Production Also by me: The TypeScript Library — the 5-book collection My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools Me: xgabriel.com | GitHub A typical TypeScript HTTP service has five layers, and most teams write the same type five times. The column lives in the database. The ORM model mirrors it. A request DTO picks a subset. A validator checks the DTO. The handler returns a response shape that lines up with the row again. Each one is hand-typed, and each one drifts. The typo that costs you Friday afternoon is between userName in the validator and username in the SQL. Drizzle, drizzle-zod, and Hono let you write that schema exactly once. The column type flows down the stack: row type, insert type, request validator, handler return, RPC client on the frontend. Five layers, one source of truth, and the compiler shouts when any of them stop matching.…