monorepo-strategy

Monorepo Deployment Strategy

Detection

A repository is a monorepo if any of these are present:

Service Discovery

Node.js monorepos

1. Read workspace configuration:
   • npm/yarn/bun: workspaces array in root package.json
   • pnpm: packages list in pnpm-workspace.yaml
2. For each workspace package, read its package.json
3. A package is a deployable service if it has a start script or a main/module entry
4. A package is a shared library if other packages depend on it but it has no start script

Go monorepos

1. Read go.work for module list
2. Each module with a main package (main.go or cmd/ directory) is deployable

Rust monorepos

1. Read root Cargo.toml → [workspace].members
2. Each member with [[bin]] target or src/main.rs is deployable

Generic (no workspace tool)

1. Scan apps/, services/, packages/ for subdirectories
2. Each subdirectory with its own manifest file (package.json, go.mod, Cargo.toml, etc.) is a potential service
3. Each subdirectory with its own Dockerfile is a deployable service

Dependency Graph

Build the service dependency graph before deploying:

1. For each service, read its dependencies on other workspace packages
2. Topologically sort: deploy dependencies before dependents
3. Shared libraries are built first (they're dependencies of services)

Node.js dependency detection

In package.json, workspace dependencies use:

• "@scope/package": "workspace:*" (pnpm)
• "@scope/package": "*" with the package in workspaces (npm/yarn)

Go dependency detection

In each module's go.mod, require directives pointing to other workspace modules (matched by module path from go.work).

Build Context

The Docker build context for monorepo services should usually be the repository root, not the service subdirectory:

services:
  api:
    build:
      context: .                    # repo root
      dockerfile: apps/api/Dockerfile  # service-specific Dockerfile

This ensures shared packages, root lockfiles, and workspace configuration are available during build.

Dockerfile for monorepo service

FROM node:22-slim AS deps
WORKDIR /app
COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
COPY apps/api/package.json ./apps/api/
COPY packages/shared/package.json ./packages/shared/
RUN corepack enable && pnpm install --frozen-lockfile

FROM deps AS build
COPY packages/shared ./packages/shared
COPY apps/api ./apps/api
RUN pnpm --filter api build

FROM node:22-slim
WORKDIR /app
COPY --from=build /app/apps/api/dist ./dist
COPY --from=build /app/node_modules ./node_modules
COPY --from=build /app/apps/api/package.json ./
EXPOSE 3001
CMD ["node", "dist/index.js"]

Key: copy ALL workspace package.json files in the deps stage so the lockfile resolves correctly.

Selective Deployment

Not every push requires deploying every service:

1. Determine which files changed (from deployment context or git diff)
2. Map changed files to affected services:
   • apps/api/** → deploy api
   • packages/shared/** → deploy ALL services that depend on shared
   • Root config (package.json, lockfile, tsconfig.json) → deploy ALL services
3. Only deploy affected services

Compose for Monorepos

Generate docker-compose.yml with one service per deployable app:

services:
  api:
    build:
      context: .
      dockerfile: apps/api/Dockerfile
    ports:
      - "3001:3001"
    depends_on:
      db:
        condition: service_healthy

  web:
    build:
      context: .
      dockerfile: apps/web/Dockerfile
    ports:
      - "3000:3000"
    depends_on:
      - api

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: app
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 3s
      retries: 5

volumes:
  pgdata:

Turborepo / Nx Considerations

If turbo.json or nx.json is present:

• Turbo: Use turbo run build --filter=<service> for targeted builds
• Nx: Use nx build <service> or nx affected --target=build for selective builds
• Both tools handle dependency ordering automatically
• In Docker: install the build orchestrator during the build stage, use it for targeted builds

Gotchas

• pnpm hoists differently than npm/yarn — --shamefully-hoist may be needed for some packages
• Root tsconfig.json with references must be present for TypeScript project references to work
• Turborepo --filter uses package names from package.json, not directory names
• Go workspaces: go.work.sum must also be committed alongside go.work
• Nx affected needs git history in the Docker build — use --base=HEAD~1 or copy .git (adds size)
• Each service in a compose file can have different environment variables — don't share .env across services that need different configs

Related Skills

• compose-setup — Base compose patterns for databases and caches
• dockerfile-generation — Ecosystem-specific Dockerfile patterns to adapt for monorepo services
• node-deploy — Node.js monorepo support (workspaces, package managers)
• go-deploy — Go workspace support