home / skills / athola / claude-night-market / architecture-paradigm-modular-monolith
/plugins/archetypes/skills/architecture-paradigm-modular-monolith
This skill helps teams structure large Python codebases into well-bounded modules with clear contracts, delivering autonomous modules without distributed
npx playbooks add skill athola/claude-night-market --skill architecture-paradigm-modular-monolithReview the files below or copy the command above to add this skill to your agents.
---
name: architecture-paradigm-modular-monolith
description: 'Single deployable with enforced module boundaries for team autonomy
without distributed complexity.
Triggers: modular-monolith, module boundaries, single deployment, team autonomy
Use when: teams need autonomy without distributed overhead
DO NOT use when: already using microservices or system is small.'
category: architectural-pattern
tags:
- architecture
- modular-monolith
- monolith
- internal-boundaries
- team-autonomy
dependencies: []
tools:
- dependency-analyzer
- module-boundary-enforcer
- refactoring-planner
usage_patterns:
- paradigm-implementation
- monolith-modernization
- team-scaling
complexity: medium
estimated_tokens: 700
---
# The Modular Monolith Paradigm
## When To Use
- Organizing large codebases into well-bounded modules
- Teams wanting microservice boundaries without distributed complexity
## When NOT To Use
- Already distributed as microservices
- Tiny applications where module boundaries add unnecessary complexity
## When to Employ This Paradigm
- When you desire team autonomy similar to that of microservices, but without the operational overhead of a distributed system.
- When release velocity is slowed by tangled dependencies between internal modules.
- When a monolithic architecture is simpler to operate today, but there is a clear need to evolve toward a service-based model in the future.
## Adoption Steps
1. **Identify Modules**: Define module boundaries that align with distinct business capabilities or Bounded Contexts from Domain-Driven Design.
2. **Encapsulate Internals**: Use language-level visibility modifiers (e.g., public/private), separate packages, or namespaces to hide the implementation details of each module.
3. **Expose Public Contracts**: Each module should expose its functionality through well-defined facades, APIs, or events. Forbid direct database table access or direct implementation calls between modules.
4. **Enforce Architectural Fitness**: Implement automated tests that fail the build if forbidden dependencies or package references are introduced between modules.
5. **Plan for Evolution**: Continuously track metrics such as change coupling and deployment scope to make informed decisions about if and when to split a module into a separate service.
## Key Deliverables
- An Architecture Decision Record (ADR) that maps module boundaries and defines the rules for any shared code.
- Formal contract documentation (e.g., OpenAPI specs, event schemas) for every interaction point between modules.
- Automated dependency checks and dedicated CI/CD jobs for each module to enforce boundaries.
## Risks & Mitigations
- **Regression to a "Big Ball of Mud"**:
- **Mitigation**: Without strict enforcement, module boundaries will inevitably erode. Treat any boundary violation as a build-breaking error and maintain a disciplined approach to code reviews.
- **Shared Database Hotspots**:
- **Mitigation**: High contention on a shared database can become a bottleneck. Introduce clear schema ownership, use view-based access to restrict data visibility, or implement data replication strategies to reduce coupling.
## Troubleshooting
### Common Issues
**Skill not loading**
Check YAML frontmatter syntax and required fields
**Token limits exceeded**
Use progressive disclosure - move details to modules
**Modules not found**
Verify module paths in SKILL.md are correct
This skill codifies the modular monolith architecture for teams that want autonomous, bounded modules inside a single deployable system. It enforces module boundaries, public contracts, and automated checks so teams can move fast without introducing distributed-system complexity. The goal is team autonomy, predictable releases, and a clear evolution path toward services if needed.
The skill defines module boundaries aligned to business capabilities and enforces them with encapsulation, facades, and CI checks. It requires formal public contracts (APIs or events) and build-time tests that fail on forbidden cross-module dependencies. It also provides guidance for ADRs, schema ownership, and metrics to track change coupling and deployment scope.
How do you prevent teams from bypassing module contracts?
Treat any cross-module direct access as a build-breaking error enforced by automated dependency checks and CI. Pair this with code review rules and visible ADRs that show ownership and allowed interactions.
Can modules share a single database?
Yes, but with strict schema ownership and access rules. Use view-based access, read replicas, or selective replication to reduce contention and enforce encapsulation.
When should a module be split into a microservice?
Split when deployment scope, independent scaling, or operational ownership outweighs the costs of distributed systems. Track metrics like change coupling, deployment frequency, and resource contention to make that decision.