# [System/Feature Name] Architecture

**Version:** 1.0
**Date:** YYYY-MM-DD
**Author:** [Your Name]
**Status:** [Draft | Review | Approved | Implemented]

---

## Overview

### Purpose
[2-3 sentences describing what this system/feature does and why it exists]

### Scope
**In Scope:**
- [Feature/capability 1]
- [Feature/capability 2]
- [Feature/capability 3]

**Out of Scope:**
- [What this will NOT do]
- [Future enhancements not in current scope]

### Success Criteria
- [ ] [Measurable criterion 1]
- [ ] [Measurable criterion 2]
- [ ] [Measurable criterion 3]

---

## Context

### Problem Statement
[Describe the problem this architecture solves]

### Current State
[Describe existing systems/architecture if applicable]

### Goals
1. [Primary goal]
2. [Secondary goal]
3. [Additional goal]

### Constraints
- **Technical:** [Technical limitations or requirements]
- **Business:** [Budget, timeline, resource constraints]
- **Regulatory:** [Compliance requirements if applicable]

---

## Architecture Design

### System Architecture Diagram

```
[Include diagram here - can be ASCII, Mermaid, or link to image]

Example:
┌─────────────┐      ┌─────────────┐      ┌─────────────┐
│   Client    │─────>│   Server    │─────>│  Database   │
└─────────────┘      └─────────────┘      └─────────────┘
```

### Component Architecture

#### Component 1: [Name]
- **Purpose:** [What this component does]
- **Responsibilities:**
  - [Responsibility 1]
  - [Responsibility 2]
- **Interfaces:**
  - Input: [What it receives]
  - Output: [What it provides]
- **Dependencies:** [What it depends on]

#### Component 2: [Name]
- **Purpose:** [What this component does]
- **Responsibilities:**
  - [Responsibility 1]
  - [Responsibility 2]
- **Interfaces:**
  - Input: [What it receives]
  - Output: [What it provides]
- **Dependencies:** [What it depends on]

[Add more components as needed]

---

## Data Flow

### Primary Workflow

```
1. [Step 1] → [Component A]
2. [Step 2] → [Component B]
3. [Step 3] → [Component C]
4. [Result/Output]
```

### Data Flow Diagram

```
[Include data flow diagram]

Example:
User Input → Validation → Processing → Storage → Response
```

### Data Models

#### Entity: [Name]
```yaml
entity_name:
  field1: type  # description
  field2: type  # description
  field3: type  # description
```

#### Entity: [Name]
```yaml
entity_name:
  field1: type  # description
  field2: type  # description
```

---

## Integration Points

### External Systems

#### Integration 1: [System Name]
- **Purpose:** [Why we integrate]
- **Type:** [API, Database, Message Queue, etc.]
- **Protocol:** [REST, GraphQL, gRPC, etc.]
- **Authentication:** [OAuth, API Key, etc.]
- **Endpoints:**
  - `GET /endpoint1` - [Description]
  - `POST /endpoint2` - [Description]
- **Error Handling:** [How errors are handled]

#### Integration 2: [System Name]
[Same structure as above]

### Internal APIs

#### API 1: [Name]
- **Base URL:** `/api/v1/resource`
- **Endpoints:**
  - `GET /resource` - List resources
  - `POST /resource` - Create resource
  - `PUT /resource/:id` - Update resource
  - `DELETE /resource/:id` - Delete resource
- **Authentication:** [Required auth method]
- **Rate Limiting:** [Limits if applicable]

---

## Configuration

### Configuration Schema

```yaml
# config.yaml
system:
  name: string              # System name
  environment: string       # dev|staging|production
  log_level: string        # debug|info|warning|error

database:
  host: string             # Database host
  port: integer            # Database port
  name: string             # Database name
  pool_size: integer       # Connection pool size

integrations:
  service_a:
    enabled: boolean       # Enable/disable integration
    endpoint: string       # Service endpoint URL
    api_key: string       # API key (from secrets)
    timeout: integer      # Request timeout in seconds

features:
  feature_x:
    enabled: boolean       # Feature flag
    settings:
      param1: value       # Feature-specific parameter
      param2: value
```

### Environment Variables

| Variable | Description | Required | Default |
|----------|-------------|----------|---------|
| `ENV` | Environment (dev/staging/prod) | Yes | dev |
| `DB_HOST` | Database hostname | Yes | - |
| `API_KEY` | External API key | Yes | - |
| `LOG_LEVEL` | Logging level | No | info |

### Configuration Override

Configuration priority (highest to lowest):
1. Environment variables
2. Command-line arguments
3. Configuration file (`config.yaml`)
4. Default values

---

## Deployment

### Architecture Tiers

- **Presentation:** [Frontend/UI components]
- **Application:** [Business logic/API layer]
- **Data:** [Database/storage layer]

### Deployment Diagram

```
[Include deployment architecture]

Example:
┌─────────────────┐
│   Load Balancer │
└────────┬────────┘
         │
    ┌────┴────┐
    │         │
┌───▼──┐  ┌──▼───┐
│ App1 │  │ App2 │
└───┬──┘  └──┬───┘
    │         │
    └────┬────┘
         │
    ┌────▼────┐
    │   DB    │
    └─────────┘
```

### Infrastructure Requirements

- **Compute:** [CPU/memory requirements]
- **Storage:** [Disk space requirements]
- **Network:** [Bandwidth/latency requirements]
- **Scaling:** [Horizontal/vertical scaling approach]

---

## Security

### Authentication & Authorization
- **User Auth:** [Method used - OAuth, JWT, etc.]
- **Service Auth:** [API keys, mutual TLS, etc.]
- **Roles:** [User roles and permissions]

### Data Security
- **Encryption at Rest:** [How data is encrypted when stored]
- **Encryption in Transit:** [TLS/SSL configuration]
- **Secrets Management:** [How secrets are stored/accessed]

### Security Boundaries
- [Boundary 1 and its protection mechanism]
- [Boundary 2 and its protection mechanism]

---

## Performance

### Performance Requirements
- **Response Time:** [Target response times]
- **Throughput:** [Requests per second]
- **Concurrency:** [Concurrent users/requests]

### Scalability Strategy
- **Horizontal Scaling:** [How to scale out]
- **Vertical Scaling:** [How to scale up]
- **Caching:** [Caching strategy]
- **Database:** [DB scaling approach]

### Performance Optimizations
- [Optimization 1]
- [Optimization 2]
- [Optimization 3]

---

## Monitoring & Observability

### Metrics
- **System Metrics:**
  - CPU usage
  - Memory usage
  - Disk I/O
  - Network I/O

- **Application Metrics:**
  - Request rate
  - Error rate
  - Response time (p50, p95, p99)
  - Active connections

- **Business Metrics:**
  - [Business-specific metric 1]
  - [Business-specific metric 2]

### Logging
- **Log Levels:** DEBUG, INFO, WARNING, ERROR, CRITICAL
- **Log Format:** JSON structured logs
- **Log Aggregation:** [Tool/service used]
- **Retention:** [Log retention policy]

### Alerting
- **Critical Alerts:**
  - [Alert 1 and threshold]
  - [Alert 2 and threshold]

- **Warning Alerts:**
  - [Alert 1 and threshold]
  - [Alert 2 and threshold]

### Tracing
- **Distributed Tracing:** [Tool used - Jaeger, Zipkin, etc.]
- **Trace Sampling:** [Sampling strategy]

---

## Testing Strategy

### Unit Testing
- **Coverage Target:** 80% minimum
- **Framework:** [Test framework used]
- **Key Areas:**
  - Business logic
  - Data transformations
  - Utility functions

### Integration Testing
- **Scope:** Component interactions
- **Framework:** [Test framework used]
- **Key Scenarios:**
  - [Scenario 1]
  - [Scenario 2]

### End-to-End Testing
- **Scope:** Complete user workflows
- **Framework:** [Test framework used]
- **Key Workflows:**
  - [Workflow 1]
  - [Workflow 2]

### Performance Testing
- **Load Testing:** [Tool and targets]
- **Stress Testing:** [Limits to test]
- **Benchmarks:** [Performance benchmarks]

---

## Architectural Decisions

### Decision 1: [Decision Title]

**Context:**
[What situation led to this decision?]

**Options Considered:**

**Option A: [Name]**
- Pros: [Benefits]
- Cons: [Drawbacks]

**Option B: [Name]**
- Pros: [Benefits]
- Cons: [Drawbacks]

**Option C: [Name]**
- Pros: [Benefits]
- Cons: [Drawbacks]

**Decision:**
Chose Option [X] because [rationale]

**Consequences:**
- [Positive consequence 1]
- [Positive consequence 2]
- [Trade-off/negative consequence]

**Validation:**
- [ ] Product Owner approved
- [ ] Architect approved
- [ ] Technical lead approved

---

### Decision 2: [Decision Title]
[Same structure as Decision 1]

---

## Risks & Mitigation

| Risk | Severity | Impact | Mitigation Strategy | Owner |
|------|----------|--------|-------------------|-------|
| [Risk 1] | High/Med/Low | [Impact description] | [How to mitigate] | [Name] |
| [Risk 2] | High/Med/Low | [Impact description] | [How to mitigate] | [Name] |
| [Risk 3] | High/Med/Low | [Impact description] | [How to mitigate] | [Name] |

---

## Dependencies

### External Dependencies
- **Library/Service 1:** [Purpose, version, license]
- **Library/Service 2:** [Purpose, version, license]

### Internal Dependencies
- **Module 1:** [What it provides, version]
- **Module 2:** [What it provides, version]

### Dependency Graph
```
[Visual representation of dependency relationships]
```

---

## Migration & Rollout

### Migration Strategy
[How to migrate from current state to new architecture]

1. **Phase 1:** [Description]
   - Timeline: [Duration]
   - Deliverables: [What gets delivered]

2. **Phase 2:** [Description]
   - Timeline: [Duration]
   - Deliverables: [What gets delivered]

3. **Phase 3:** [Description]
   - Timeline: [Duration]
   - Deliverables: [What gets delivered]

### Rollback Plan
[How to rollback if issues arise]

1. [Rollback step 1]
2. [Rollback step 2]
3. [Rollback step 3]

---

## Open Questions

- [ ] [Question 1 that needs resolution]
- [ ] [Question 2 that needs resolution]
- [ ] [Question 3 that needs resolution]

---

## Approvals

| Role | Name | Signature | Date |
|------|------|-----------|------|
| Product Owner | | | |
| Architect | | | |
| Tech Lead | | | |
| Security | | | |

---

## References

- [Link to related design doc]
- [Link to API documentation]
- [Link to external resource]

---

## Appendix

### Glossary
- **Term 1:** Definition
- **Term 2:** Definition

### Additional Diagrams
[Any supplementary diagrams]

### Code Examples
```python
# Example implementation snippet
def example_function():
    """Demonstrates key architectural pattern"""
    pass
```

---

**Document History**

| Version | Date | Author | Changes |
|---------|------|--------|---------|
| 1.0 | YYYY-MM-DD | [Name] | Initial version |