Tech Due Diligence ARCH-1: System Architecture and Design Patterns

Start by documenting your current system architecture with clear diagrams. Show high-level components and their responsibilities, communication patterns between them (synchronous, asynchronous, event-driven), data stores and which components access them, external integrations, and deployment topology.

Make sure the architecture follows established design principles: separation of concerns (each component has a clear, focused responsibility), loose coupling (components interact through well-defined interfaces, not internal implementation details), high cohesion (related functionality is grouped together), and dependency inversion (business logic does not depend on infrastructure details).

For monolith architectures, structure them with clear module boundaries. A modular monolith with defined domains is often the ideal choice for companies that have not yet reached the scale requiring microservices. Define module interfaces and prevent cross-module database access.

For microservices, each service should own its data (no shared databases), have a clear bounded context, deploy independently, communicate through well-defined APIs or events, and run its own CI/CD pipeline. Watch out for the "distributed monolith" anti-pattern where services are tightly coupled despite being separately deployed.

Maintain Architecture Decision Records (ADRs) for significant choices. Each ADR should capture the context (what problem were you solving), the decision and rationale, the trade-offs accepted, and the current status (proposed, accepted, deprecated).

Finally, evaluate whether the current architecture can handle 3-5x current load without a fundamental redesign. Identify bottlenecks and build a roadmap to address them before they become critical.