Purpose
To define clear standards for designing services and modular components, ensuring systems are scalable, maintainable, and reusable across projects.
This avoids monolith sprawl, reduces duplication, and promotes clean separation of concerns.
Scope
- Applies to all backend services, APIs, and shared libraries.
- Used by Developers, Tech Leads, Architects, and DevOps.
- Covers service boundaries, modular design, reusability, versioning, and deprecation.
Principles
- Single Responsibility – Each service/module must serve one well-defined purpose.
- Separation of Concerns – UI, API, business logic, and persistence must be separated.
- Interoperability – Services communicate through well-defined contracts (API/Events).
- Reusability First – Common logic (auth, logging, notifications) must be extracted into shared modules/packages.
- Loose Coupling & High Cohesion – Internal modules should be tightly cohesive, but services must be loosely coupled.
- Backward Compatibility – Existing consumers should not be due to upgrade.
Rules & Standards
Service Design Rules
| Area | Policy Standard |
| Service Boundaries | Must align with business domains (e.g., User, Payments, Booking). |
| APIs | Must follow API Contract Template (Doc 4). |
| Data Ownership | Each service owns its DB schema (no cross-service DB access). |
| Communication | Prefer asynchronous events over direct sync calls for non-critical flows. |
| Failure Isolation | Services must fail gracefully (timeouts, retries, circuit breakers). |
Modularity Rules
| Area | Policy Standard |
| Code Reuse | Shared logic extracted into internal packages (Doc 5/6). |
| Structure | Adopt layered architecture (Controller → Service → Repository). |
| Naming | Modules named based on domain function (e.g., user-service, booking-engine). |
| Dependencies | No circular dependencies across modules. |
| Testing | Each module must have unit + integration test coverage ≥70%. |
Versioning & Deprecation
- All services/modules must follow SemVer (Doc 13 – Versioning Policy).
- Deprecated services must:
- Be marked in README + Catalog.
- Provide a migration path.
- Have EOL timeline (≥6 months).
Governance
- Review: All new services/modules must undergo Architecture Review (Doc 3).
- Ownership: Each service must have a documented owner team.
- Audit: Quarterly audit of service boundaries + modularity compliance.
- Exceptions: Any deviation requires approval from Tech Council/CTO.