System Design Document Generator

You are a staff engineer writing a design document for a new system. Create a comprehensive design doc that a team can implement from.

System to design: [SYSTEM_DESCRIPTION]
Problem being solved: [PROBLEM]
Scale requirements: [SCALE_REQUIREMENTS]
Team context: [TEAM_CONTEXT]
Timeline: [TIMELINE]
Existing systems to integrate with: [EXISTING_SYSTEMS]

Write a design document:

## 1. Overview
- **Problem Statement**: What we're solving and for whom
- **Goals**: What success looks like (measurable)
- **Non-Goals**: What we're explicitly NOT doing (prevents scope creep)
- **Background**: Context a new team member would need

## 2. Proposed Design

### High-Level Architecture
- System component diagram (describe each box and arrow)
- Request flow for the 2-3 most important user journeys
- Data flow diagram
- Where this fits in the broader system landscape

### Detailed Design
For each major component:
- Responsibility and interfaces
- Technology choice with rationale
- Data model (key entities and relationships)
- API contracts (key endpoints, request/response shapes)

### Data Design
- Storage technology and rationale
- Schema design for core entities
- Data access patterns
- Indexing strategy
- Data retention and archival

### Infrastructure
- Deployment topology
- Scaling strategy (horizontal/vertical, auto-scaling triggers)
- Configuration management
- Environment strategy (dev, staging, prod)

## 3. Cross-Cutting Concerns
- **Security**: Authentication, authorization, encryption, secrets management
- **Observability**: Logging, metrics, tracing, alerting, dashboards
- **Error Handling**: Failure modes, retry strategies, dead letter queues, circuit breakers
- **Performance**: Latency targets, throughput targets, caching strategy

## 4. Alternatives Considered
- For each major design choice, what else was considered and why it was rejected

## 5. Risks & Mitigations
| Risk | Likelihood | Impact | Mitigation |

## 6. Implementation Plan
- Phase 1: MVP (what and when)
- Phase 2: Production hardening
- Phase 3: Scale and optimize
- Dependencies and blockers
- Migration plan (if replacing existing system)

## 7. Open Questions
- Decisions that still need to be made
- Who needs to weigh in

## 8. Appendix
- Back-of-envelope calculations (storage, throughput, cost)
- Glossary of terms
- References