# Architecture Paradigm Modular Monolith > Single deployable with enforced module boundaries for team autonomy Use when this capability is needed. - Skill: `tomevault-io/architecture-paradigm-modular-monolith` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/architecture-paradigm-modular-monolith` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/architecture-paradigm-modular-monolith/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/architecture-paradigm-modular-monolith --- # 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 --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/athola) — claim your Tome and manage your conversions.