4. SYSTEM ARCHITECTURE & TECHNICAL DESIGN

Connected to: Section 3 (Scope), Section 5 (Timeline), Section 7 (Risk Management), Section 12 (Documentation)

Architecture Vision Statement

[A 2-3 paragraph narrative describing your system architecture at a high level - how components interact, what problems it solves, design philosophy]

Example: "[Your Product Name] is a [system type] that [primary purpose]. It eliminates the need for [complex process users currently do]. The architecture comprises [number] layers: (1) [Layer 1 description], (2) [Layer 2 description], and (3) [Layer 3 description]. The system prioritizes [key value proposition] by [how you achieve it], while allowing power users to customize via [customization method]. All components are decoupled through well-defined interfaces, enabling independent scaling and maintenance."

High-Level System Architecture

Visual Architecture Diagram

ASCII Architecture Diagram (Alternative)

┌─────────────────────────────────────────────────────────┐
│                  USER/CLIENT                             │
└─────────────────────────────────────────────────────────┘
                            │
                            ▼
┌─────────────────────────────────────────────────────────┐
│              [Your Product Name] Application           │
│  ┌─────────────┬──────────────┬───────────────────┐    │
│  │ Core API    │ Admin Panel  │ Config Manager    │    │
│  └─────────────┴──────────────┴───────────────────┘    │
└─────────────────────────────────────────────────────────┘
                            │
                            ▼
┌─────────────────────────────────────────────────────────┐
│           [Business Logic Layer]                       │
│  ┌─────────────┬──────────────┬───────────────────┐    │
│  │ [Service 1] │ [Service 2] │ [Service 3]       │    │
│  └─────────────┴──────────────┴───────────────────┘    │
└─────────────────────────────────────────────────────────┘
                            │
                            ▼
┌─────────────────────────────────────────────────────────┐
│         [Data & Integration Layer]                      │
│  ┌──────────┬──────────┬──────────┬─────────────────┐  │
│  │[Database]│[Cache]   │[External]│ [Others...]     │  │
│  └──────────┴──────────┴──────────┴─────────────────┘  │
└─────────────────────────────────────────────────────────┘
                            │
                            ▼
┌─────────────────────────────────────────────────────────┐
│              [Core Business Logic Layer]                │
│  ┌──────────────────────────────────────────────────┐  │
│  │  [Component 1]                                   │  │
│  │  - [Feature 1]                                   │  │
│  │  - [Feature 2]                                   │  │
│  │  - [Feature 3]                                   │  │
│  │  - [Event System]                                │  │
│  └──────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────┘
                            │
                            ▼
┌─────────────────────────────────────────────────────────┐
│              [External Services / Infrastructure]        │
│  ([Service A], [Service B], [Service C], etc.)          │
└─────────────────────────────────────────────────────────┘

Component Specification

Component 1: [Component Name] (Technology Stack)

Purpose: [Primary purpose of this component - what it does for users]

Responsibilities:

• [Responsibility 1 - e.g., User interface and interaction]
• [Responsibility 2 - e.g., Configuration parsing and validation]
• [Responsibility 3 - e.g., Core functionality execution]
• [Responsibility 4 - e.g., Data processing and transformation]
• [Responsibility 5 - e.g., Event handling and notifications]
• [Responsibility 6 - e.g., Error handling and retry logic]
• [Responsibility 7 - e.g., Telemetry and logging]

Key Interfaces:

class [ComponentName] {
  [method1](): Promise<[ReturnType]>
  [method2](params: [ParamType]): Promise<[ReturnType]>
  [method3](): Promise<[ReturnType]>
  [method4](handler: [HandlerType]): void
  [method5](params: [ParamType]): Promise<void>
}

Dependencies:

• [Dependency 1 - e.g., Library for core functionality]
• [Dependency 2 - e.g., TypeScript for type safety]
• [Dependency 3 - e.g., Testing framework]

Technology Stack:

• Language: TypeScript
• Runtime: Node.js 18+
• Package Manager: npm/yarn
• Distributed As: [Distribution method, e.g., npm package @your-org/product-name]

Performance Requirements:

• [Operation 1]: <[time] seconds
• [Operation 2]: <[time] milliseconds
• [Operation 3]: <[time] milliseconds latency

Component 2: [Component Name] (Business Logic)

Purpose: [Core business logic and processing layer]

Responsibilities:

• [Responsibility 1 - e.g., Data processing and transformation]
• [Responsibility 2 - e.g., Business rule enforcement]
• [Responsibility 3 - e.g., Workflow orchestration]
• [Responsibility 4 - e.g., Event handling and notifications]
• [Responsibility 5 - e.g., Performance optimization]

Key Classes/Modules:

[MainClass] (Core business logic)

class [MainClass] {
  // [Property description]
  private [property]: [Type];
  
  // [Method description]
  [method1](params: [ParamType]): Promise<[ReturnType]>;
  
  // [Method description]
  [method2](params: [ParamType]): Promise<[ReturnType]>;
  
  // [Method description]
  [method3](key: string): Promise<[ReturnType]>;
  
  // [Method description]
  [method4](key: string, value: [Type]): Promise<void>;
}

[FactoryClass] (Object creation)

class [FactoryClass] {
  [createMethod](params: [ParamType]): Promise<[ReturnType]>;
}

Technology Stack:

• Language: [Language, e.g., TypeScript, Python, Java, etc.]
• Framework: [Framework, e.g., Express, FastAPI, Spring, etc.]
• Standards: [Relevant standards or patterns]
• Performance Target: <[X] ms per operation, <[Y] ms per request

Quality Requirements:

• 80%+ test coverage (unit + integration)
• Code review required for all changes
• Performance benchmarks met

Component 3: [Component Name] (Data & Integration)

Purpose: [Data management and external service integration]

Responsibilities:

• [Responsibility 1 - e.g., Database connection and query management]
• [Responsibility 2 - e.g., External API integration]
• [Responsibility 3 - e.g., Data caching and optimization]
• [Responsibility 4 - e.g., Service registry and discovery]
• [Responsibility 5 - e.g., Error handling and retry logic]

Supported Integrations:

Integration Interface:

interface [IntegrationInterface] {
  name: string;
  endpoint: string;
  [method1](params: [ParamType]): Promise<[ReturnType]>;
  [method2](params: [ParamType]): Promise<[ReturnType]>;
  [method3](id: string): Promise<[ReturnType]>;
  [method4](params: [ParamType]): Promise<[ReturnType]>;
}

Component 4: [Component Name] (Admin/Management Interface)

Purpose: [Administrative interface for system management]

Responsibilities:

• [Responsibility 1 - e.g., User and role management]
• [Responsibility 2 - e.g., System configuration]
• [Responsibility 3 - e.g., Monitoring and analytics]
• [Responsibility 4 - e.g., Deployment and release management]
• [Responsibility 5 - e.g., Log viewing and troubleshooting]

Key Features:

# Initialize new project/environment
[command] init [project-name]

# Deploy to staging
[command] deploy --environment staging

# Deploy to production
[command] deploy --environment production

# Update configuration
[command] config --key "setting-name" --value "setting-value"

# Run tests
[command] test --config config.yaml

# View logs
[command] logs --service service-name

# Generate code/documentation
[command] generate --source ./source

Component 5: API & Event System

Purpose: [API endpoints and real-time event handling]

Responsibilities:

• [Responsibility 1 - e.g., Webhook delivery for events]
• [Responsibility 2 - e.g., REST API for queries]
• WebSocket support for real-time updates
• Event filtering and aggregation

API Endpoints:

Event Types:

• [Event1] - [Event description]
• [Event2] - [Event description]
• [Event3] - [Event description]
• Error - [Error event description]

Architecture Decisions (ADRs)

ADR-001: [Architecture Decision Title]

Status: [Proposed / Accepted / Deprecated]

Context: [Problem statement and question]. Two approaches:

1. Option 1: [Description] ([pros], [cons])
2. Option 2: [Description] ([pros], [cons])

Decision: [Selected approach]

Rationale:

• [Reason 1 - e.g., 90% of users want pre-built solutions]
• [Reason 2 - e.g., Faster time-to-market]
• [Reason 3 - e.g., Standardized patterns improve maintainability]
• [Reason 4 - e.g., Power users can still customize when needed]

Consequences:

• ✅ [Positive consequence 1]
• ✅ [Positive consequence 2]
• ❌ [Negative consequence 1]
• ❌ [Negative consequence 2]

Trade-offs:

• Chose [priority] over [alternative priority]
• Can add [future enhancement] later if needed

ADR-002: [Architecture Decision Title]

Status: [Proposed / Accepted / Deprecated]

Context: Should [Product Name] support [multiple options] or focus on [single option] initially?

Alternatives:

1. Option 1: [Description]
2. Option 2: [Description]
3. Option 3: [Description]

Decision: [Selected option]

Rationale:

• [Reason 1 - e.g., Users want flexibility]
• [Reason 2 - e.g., Architecture supports multiple options]
• [Reason 3 - e.g., Reduces vendor lock-in]
• [Reason 4 - e.g., Covers majority of use cases]

Consequences:

• ✅ [Positive consequence 1]
• ✅ [Positive consequence 2]
• ❌ [Negative consequence 1]
• ❌ [Negative consequence 2]

Trade-offs:

• Chose [priority] over [alternative priority]
• Will add [future enhancement] based on user demand

ADR-003: [Architecture Decision Title]

Status: [Proposed / Accepted / Deprecated]

Context: [Problem statement and question]. Two approaches:

1. Option 1: [Description] ([pros], [cons])
2. Option 2: [Description] ([pros], [cons])

Decision: [Selected approach with fallback strategy]

Rationale:

• [Reason 1 - e.g., Enables advanced features]
• [Reason 2 - e.g., Aligns with industry standards]
• [Reason 3 - e.g., Better user experience]
• [Reason 4 - e.g., Fallback ensures compatibility]

Consequences:

• ✅ [Positive consequence 1]
• ✅ [Positive consequence 2]
• ❌ [Negative consequence 1]
• ❌ [Negative consequence 2]

Trade-offs:

• Chose [priority] over [alternative priority]
• [Fallback strategy] minimizes risk

ADR-004: [Architecture Decision Title]

Status: [Proposed / Accepted / Deprecated]

Context: Should [Product Name] support [single technology] or [multiple technologies]?

Decision: [Selected approach with future expansion plan]

Rationale:

• [Reason 1 - e.g., Primary technology has best ecosystem]
• [Reason 2 - e.g., Targeting specific developer segment first]
• [Reason 3 - e.g., Technology has best tooling for our use case]
• [Reason 4 - e.g., Multi-technology support can be added later]

Consequences:

• ✅ [Positive consequence 1]
• ✅ [Positive consequence 2]
• ❌ [Negative consequence 1]
• ❌ [Negative consequence 2]

Trade-offs:

• Chose [priority] over [alternative priority]
• [Future technology] support planned for [phase] based on demand

ADR-005: [Architecture Decision Title]

Status: [Proposed / Accepted / Deprecated]

Context: [Problem statement and question]. Trade-off between [option 1] and [option 2].

Decision: [Selected approach]

Rationale:

• [Reason 1 - e.g., License allows commercial use]
• [Reason 2 - e.g., Community contributions improve codebase]
• [Reason 3 - e.g., Alternative revenue streams available]
• [Reason 4 - e.g., Aligns with community values]

Consequences:

• ✅ [Positive consequence 1]
• ✅ [Positive consequence 2]
• ❌ [Negative consequence 1]
• ❌ [Negative consequence 2]

Trade-offs:

• Chose [priority] over [alternative priority]
• Will monetize through [alternative revenue model]

Non-Functional Requirements

Performance

Security

Reliability

Scalability

Maintainability

Technology Stack Summary

This architecture is your technical north star. Decisions made here cascade to all implementation work.

Connected to: Section 3 (Scope), Section 5 (Timeline), Section 6 (Resources), Section 8 (Execution)