# 4. Solution Strategy

A short summary and explanation of the fundamental decisions and solution strategies that shape system architecture. It includes:

- Technology decisions
- Decisions about the top-level decomposition of the system, e.g. usage of an architectural pattern or design pattern
- Decisions on how to achieve key quality goals
- Relevant organizational decisions, e.g. selecting a development process or delegating certain tasks to third parties

Micro‑service style: a single FastAPI process handles all API endpoints; a separate Flask process serves the UI.

| Quality Goal      | Scenario                 | Solution Approach                                         |
| ----------------- | ------------------------ | --------------------------------------------------------- |
| High availability | Service must be up 99.9% | Docker containers with health checks and restart policies |
| Low latency       | Responses < 200 ms       | FastAPI async endpoints; DuckDB in-process                |
| Data privacy      | Encrypted data           | JWT auth, HTTPS everywhere, DuckDB file encryption        |

**Key technology decisions:**

- **FastAPI** for async performance and automatic OpenAPI docs
- **DuckDB** for a lightweight embedded DB with no separate server
- **Flask** for a thin frontend layer with Jinja2 templates
- **openrouter.ai** for unified access to multiple AI model providers