Technical Solution & Architecture Breakdown

There is a prompt instruction at https://www.zangwei.dev/prompts/product-execution/technical-solution-architecture-design-prompt . Extract and follow the prompt to create file /docs/handbook/product/{version|feature}/tech.md

You are a senior Tech Lead / Architect. Design the **Technical Solution & Architecture Breakdown** for the current version.

## Positioning
The goal is not the most optimal or complex architecture. It is to answer:
1) Is this PRD feasible under current technical constraints?
2) How do we implement it with minimal complexity and controllable risk?
3) Where are the key technical risks and what are the fallbacks?

This is the technical decision document bridging PRD -> implementation.

## Preconditions
- A clear PRD exists (features, interaction, logic, acceptance)
- Product boundaries and MVP scope are defined
- Cover only the current version; do not over-design for hypothetical future

## General requirements
- Prefer simple, mature, controllable solutions
- Explain trade-offs; do not choose complexity just because it looks advanced
- Architecture must support current success criteria, not imaginary scale
- If risk is unacceptable, call it out explicitly

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## Output structure

1) Goals & constraints
- PRD scope covered by this solution
- Key NFRs (performance, reliability, security, compliance)
- Technical constraints (time, staffing, existing systems, budget)

2) High-level architecture
- Overall architecture overview (text or module diagram description)
- Core modules and responsibilities
- Data flow and call relationships
- Identify modules as:
  - core path
  - supporting
  - replaceable

3) Core flows & key technical points
- Implementation mapping for key business flows
- sync/async strategy
- state management approach
- consistency and failure-handling approach
- Mapping from PRD interaction/logic to technical design

4) Data design & storage
- Core data objects and relationships
- Storage choices (DB/cache/object storage)
- Data lifecycle and constraints
- Privacy/security handling strategy

5) Interfaces & integrations
- Internal interface design principles
- External dependencies (APIs, models, payments, auth)
- Stability and degradation strategies
- Mocks/stubs/substitutes for development and fallback

6) Technical risks & mitigations
- Major risk points for this version
- Likelihood and blast radius
- Mitigation/avoidance (degrade, limit, substitute, postpone)
- Which risks are acceptable vs unacceptable

7) Scalability & tech-debt control
- Short-term scaling strategy
- Intentional tech debt areas (explicit)
- Possible evolution direction (no detailed design)

8) Alignment with execution plan
- How to break this solution into dev tasks
- Parallelizable vs dependent parts
- Key impacts on schedule and resourcing

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## Output requirements
- No code
- Do not drown in details or future design
- Must be understandable and implementable by the engineering team
- If a PRD requirement is infeasible or too risky, call it out and propose alternatives

End with 3–5 bullet points:
"Is this solution simple, feasible, and risk-controlled enough for the current stage?"