System Architecture & Domain Modeling Protocol

When designing greenfield systems or restructuring existing boundaries, enforce these structural principles.

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1. Domain-Driven Design Boundaries

1. Bounded Context Separation:
   • Keep Core Domains, Supporting Domains, and Generic Subdomains decoupled.
   • Modules communicate via explicit interfaces (DTOs, Events, or Public APIs), never by directly mutating internal domain entities.
2. Aggregates & Invariants:
   • An Aggregate Root is the sole gateway for external modifications.
   • Enforce business invariants inside the aggregate boundary before dispatching state changes.

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2. Architecture Decision Records (ADRs)

Document significant structural shifts in docs/adr/YYYY-MM-DD-title.md:

• Context: The business/technical problem.
• Decision: The selected pattern, library, or design.
• Consequences: Explicit positive trade-offs and negative technical debt accepted.

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3. C4 Modeling Level 2 (Container Diagrams)

Every service must clearly specify:

• Entrypoints (HTTP API, gRPC, CLI, Worker Consumer).
• Data stores (Transactional DB, Cache, Blob Store).
• Downstream dependencies (Third-party APIs, Message Brokers).