Nx Monorepo
Nx is a build system optimized for monorepos. Combined with hexagonal architecture, it enforces the boundaries that keep code maintainable as systems scale.
Why Nx for Hex
Hexagonal architecture separates domain logic from infrastructure. Nx enforces this separation through library boundaries:
apps/ → Entry points (Next.js, NestJS)
libs/
domain/ → Business logic, entities, use cases
ports/ → Interfaces (what the domain needs)
adapters/ → Implementations (databases, APIs, UI)
shared/ → Utilities, types, constants
The dependency rule: adapters depend on ports depend on domain. Nx's @nx/enforce-module-boundaries lint rule makes this a build error, not a code review comment.
Library Types
| Type | Hex Layer | Contains |
|---|---|---|
| feature | Adapters | Smart components with data access |
| ui | Adapters | Presentational components |
| data-access | Adapters | API clients, state management |
| domain | Domain | Entities, use cases, business rules |
| util | Shared | Low-level utilities |
Key Commands
# Visualize dependencies
nx graph
# Run affected tests only
nx affected --target=test
# Generate library with boundaries
nx g @nx/react:lib auth --directory=domain
Why This Matters
- Caching — Nx only rebuilds what changed
- Boundaries — Architecture violations fail the build
- Scaling — Add apps without duplicating domain logic
- AI-assisted dev — Clear structure helps AI understand the codebase
Resources
Context
- Clean Architecture — Hex layers enforced by Nx boundaries
- Engineering Quality Benchmarks — Module budgets, dependency graph health thresholds
- Engineering Anti-Patterns — Barrel blowouts, config drift, boundary violations
- NestJS
Questions
Which engineering decision related to this topic has the highest switching cost once made — and how do you make it well with incomplete information?
- At what scale or complexity level does the right answer to this topic change significantly?
- How does the introduction of AI-native workflows change the conventional wisdom about this technology?
- Which anti-pattern in this area is most commonly introduced by developers who know enough to be dangerous but not enough to know what they don't know?