railway-docs

Railway supports isolated monorepos via the Root Directory setting and shared monorepos via custom build and start commands. For shared TypeScript workspaces, leave root directory empty and use commands like pnpm --filter backend build, plus watch paths to avoid unnecessary rebuilds.

Set variables by applying an EnvironmentConfig JSON patch with the CLI command railway environment edit --json. Variables support references like ${{shared.DOMAIN}} or ${{Postgres.DATABASE_URL}} to wire services together, and setting a variable to null deletes it.

Railpack auto-detects Node, Python, Go, PHP, Java, Ruby, Rust, Elixir, Gleam, Deno, and static sites. It recognizes frameworks like Next.js, Vite, Astro, Django, and FastAPI, generating appropriate build and start commands without configuration.

Use private domains for service-to-service and service-to-database communication since they are faster, avoid egress costs, and are more secure. Use public domains only when browsers or external webhooks need access, since they cannot reach the private network.

Setting a root directory makes code outside that directory unavailable during builds, breaking imports from shared packages. Remove the root directory and use workspace filter commands like pnpm --filter or turbo run build --filter instead.