| name | tech-stack-advisor |
| description | Recommend a technology stack based on project requirements, team constraints, and non-functional requirements. Use when Dev needs to make and justify technology choices for frontend, backend, database, and infrastructure with documented rationale and trade-offs. |
| inclusion | manual |
Tech Stack Advisor
Recommend a technology stack for a project based on its requirements, team context, and constraints — with explicit rationale and documented alternatives for each choice.
When to Use
- Dev is starting architecture design and needs to select technologies
- Stakeholders need a justified tech stack decision before implementation
- Evaluating trade-offs between multiple viable options
Input
projectType: "Web SaaS application with mobile support"
teamSize: 5
teamExpertise: "React, Node.js, some Python"
scalingRequirements: "1,000 concurrent users at launch, 10x growth in 12 months"
keyConstraints: "3-month deadline, limited DevOps capacity"
nonFunctionalRequirements:
- "< 200ms API response time"
- "99.9% uptime"
- "GDPR compliance"
Output Format
## Tech Stack Recommendation: {Project Name}
### Summary
| Layer | Selected | Rationale Summary |
|-------|----------|-------------------|
| Frontend | React + TypeScript | Team expertise, ecosystem maturity |
| Backend | Node.js (Express/Fastify) | Shared language with frontend, team familiarity |
| Database | PostgreSQL | Relational data model, GDPR compliance features |
| Cache | Redis | Session management, API response caching |
| Infrastructure | Docker + Railway/Render | Low DevOps overhead, fast deployment |
| Auth | Auth.js / Clerk | Reduces implementation time, security best practices |
### Detailed Decisions
#### Frontend: React + TypeScript
- **Rationale**: Team has existing React expertise; TypeScript reduces runtime errors in a 3-month timeline
- **Alternative considered**: Vue 3 — comparable DX but lower team familiarity increases ramp-up risk
- **Trade-off**: Larger bundle size vs. Next.js SSR, acceptable for SaaS dashboard use case
#### Backend: Node.js + Fastify
- **Rationale**: Shared language reduces context switching; Fastify outperforms Express by ~2x for JSON throughput
- **Alternative considered**: Python/FastAPI — better for ML workloads but no current ML requirements
- **Trade-off**: Single-threaded model requires careful async handling for CPU-intensive tasks
#### Database: PostgreSQL
- **Rationale**: ACID compliance for transactional data; row-level security supports GDPR data isolation
- **Alternative considered**: MongoDB — flexible schema but weaker consistency guarantees for financial data
- **Trade-off**: Schema migrations require more planning than document stores
### Scaling Plan
| Phase | Users | Architecture Change |
|-------|-------|---------------------|
| Launch | ~1,000 | Single server, vertical scaling |
| 6 months | ~5,000 | Read replicas, Redis caching layer |
| 12 months | ~10,000 | Horizontal scaling, CDN, queue-based async jobs |
Decision Criteria
| Factor | Weight | Notes |
|---|
| Team expertise | High | Unfamiliar tech adds 20–40% time overhead |
| Timeline fit | High | Avoid technologies requiring >1 week ramp-up |
| Scaling headroom | Medium | Must support 10x without full rewrite |
| Community/ecosystem | Medium | Active ecosystem = faster problem resolution |
| Operational complexity | Medium | Match DevOps capacity of the team |
| License/cost | Low | Flag any non-OSS or usage-based cost surprises |
Execution Rules
- Every technology choice must include: rationale, one alternative considered, and the trade-off accepted
- Flag any choice that conflicts with stated constraints (deadline, team size, expertise)
- Include a scaling plan showing when architecture changes are needed
- Do not recommend technologies the team has zero experience with unless the alternative is clearly worse
- If requirements are contradictory (e.g. "no DevOps capacity" + "Kubernetes"), flag the conflict explicitly
