| name | architecture-monolith |
| description | Modular monolith architecture workflow for strong domain boundaries, transactional consistency, and operational simplicity in a single deployable. Use when teams need fast delivery and coherent data consistency with controlled complexity; do not use when independent runtime scaling boundaries are mandatory. |
Architecture Monolith
Overview
Use this skill to design modular monoliths that preserve internal autonomy without introducing distributed-system overhead.
Scope Boundaries
- Product scope or team size favors a single deployable unit.
- Cross-domain workflows require strong transactional consistency.
- Operational simplicity is a top constraint.
Core Judgments
- Module boundaries: domain cohesion and dependency direction inside one codebase.
- Internal contracts: which module APIs are allowed and how enforced.
- Data ownership in shared database: logical ownership and write access discipline.
- Future extraction seams: where boundaries should support later service splits.
Practitioner Heuristics
- Treat modules like products with stable public interfaces.
- Forbid cross-module database writes except through explicit module APIs.
- Keep shared kernel minimal and intentionally versioned.
- In dynamic languages, define explicit module interface types to avoid ad hoc maps and pervasive casts at boundaries.
Workflow
- Partition core domains into modules with clear responsibility.
- Define allowed dependency directions and anti-corruption boundaries.
- Specify module-level contracts for commands, queries, and events.
- Align transactional scope with module invariants.
- Add observability by module to expose coupling hotspots.
- Record extraction candidates and triggers for future decomposition.
Common Failure Modes
- Modular monolith degrades into "big ball of mud" via unrestricted imports.
- Shared tables bypass module contracts and break ownership.
- Runtime simplicity hides growing conceptual complexity.
Failure Conditions
- Stop when module boundaries cannot be enforced in code review/tooling.
- Stop when critical invariants span modules without clear ownership.
- Escalate when required independent scaling/deployment is no longer feasible.
