Architecture Pattern Selection

Purpose

Select appropriate architectural patterns (monolith, microservices, event-driven, etc.) based on requirements, constraints, and trade-offs to create a sustainable system design.

When to Use

• New project architecture design
• Major system evolution
• Scalability challenges
• Technology modernization

Prerequisites

• Requirements understood
• NFRs quantified
• Constraints identified
• Team capabilities known

Process

Step 1: Analyze Requirements

Key questions:
- What are the scalability needs?
- How complex is the domain?
- What are the deployment constraints?
- What is the team's experience?
- What are the performance requirements?

Step 2: Evaluate Pattern Options

Common patterns:
- Monolithic: Simple, single deployment
- Layered: Separation of concerns
- Microservices: Independent scaling
- Event-Driven: Async, loose coupling
- Serverless: Pay-per-use, managed
- CQRS: Read/write optimization

Step 3: Apply Selection Criteria

Selection matrix:
| Criteria | Monolith | Microservices | Serverless |
|----------|----------|---------------|------------|
| Complexity | Low | High | Medium |
| Scalability | Limited | High | High |
| Team size | Small | Large | Any |
| Time to market | Fast | Slow | Fast |
| Operational cost | Low | High | Variable |

Step 4: Document Decision

Create ADR with:
- Context and requirements
- Options considered
- Decision and rationale
- Trade-offs accepted
- Consequences

Step 5: Define Pattern Implementation

For chosen pattern:
- Component boundaries
- Communication patterns
- Data management approach
- Deployment strategy
- Evolution path

Inputs

Input	Type	Required	Description
requirements_spec	Markdown	Yes	System requirements
nfr_matrix	Markdown	Yes	Performance/scale needs
constraints	Markdown	Yes	Technical constraints

Outputs

Output	Type	Description
architecture_pattern.md	Markdown	Pattern decision
ADR-001	Markdown	Architecture decision record
component_diagram	Mermaid	High-level components

StudyAbroad-Specific Considerations

• Modular monolith recommended for MVP (team size, time to market)
• Event-driven for external API integrations
• Consider serverless for document processing
• Plan for future microservices extraction

Integration Points

• Requirements Agent: NFRs input
• Security Agent: Security architecture patterns
• DevOps Agent: Deployment patterns

Examples

Architecture Pattern Decision - StudyAbroad-v1

Context:
- MVP timeline: 6 months
- Team size: Small (2-3 developers)
- Scale: 10K concurrent users (peak)
- Domain: Moderately complex

Options Evaluated:
1. Monolithic - Fast development, limited scale
2. Modular Monolith - Balanced approach
3. Microservices - Overkill for MVP

Decision: Modular Monolith

Rationale:
- Faster time to market
- Sufficient for initial scale
- Clear module boundaries for future extraction
- Team can manage single deployment

Modules Identified:
├── User Module (auth, profile)
├── University Module (search, details)
├── Application Module (forms, documents)
├── Notification Module (email, alerts)
└── Integration Module (external APIs)

Evolution Path:
- Phase 1: Modular monolith (MVP)
- Phase 2: Extract Integration Module (if API scaling needed)
- Phase 3: Consider microservices for high-traffic modules

Validation

• Pattern aligns with requirements
• Team can implement pattern
• Scalability needs addressed
• ADR documented
• Evolution path defined