Assessment Brief
Technical Assessment — Technical Lead
1. Strategic Context
Company: PhoenixDX — AI-first engineering hub, Ho Chi Minh City
Mission: Re-architect mission-critical enterprise systems with AI-augmented engineering practices
Product A — A domain-rich enterprise platform used by ~40,000 users globally, covering:
- Travel booking (Expedia-like)
- Event planning & management
- Workforce management
- Digital payments & automated booking
- Allocation algorithms
- Centralised communications
Current State: Legacy .NET monolith
Target State: Modern microservices platform
2. Target Tech Stack
| Layer | Technology |
|---|---|
| Backend | .NET 8 Microservices |
| Frontend | React 18 + Shared Design System |
| Messaging | Azure Service Bus (Event-driven) |
| Database | Per-service databases (decomposed from monolith) |
| Infrastructure | CI/CD + IaC |
| Observability | Logging, monitoring, tracing |
| Data | AI-ready data foundation |
3. Constraints
| Constraint | Detail |
|---|---|
| Users | 40,000 active global users |
| Availability | Zero downtime during migration |
| Payment | Payment flow cannot change in Phase 1 |
| Team Size | 5 engineers only |
| Timeline | 9 months total |
4. Deliverables
4.1 Target Architecture Overview
- High-level architecture diagram
- Service boundaries definition (bounded contexts)
- Communication model (sync/async, API gateway, event bus)
4.2 Migration Strategy
- Phased approach — minimum 4 phases
- Zero-downtime strategy — how to prevent downtime during migration
- Backward compatibility plan — how legacy and new systems coexist
4.3 Failure Modeling
- Identify 5 high-risk failure scenarios
- For each scenario, provide:
- Likelihood: Low / Medium / High
- Impact: Low / Medium / High
- Mitigation strategy
4.4 Trade-Off Log
- What are you intentionally not optimizing?
- What technical debt are you accepting?
- What would you revisit in 6 months?
4.5 Assumptions
- List at least 8 explicit assumptions
4.6 AI Usage Declaration
- What AI tools were used during this exercise
- What sections were AI-assisted
- What was manually validated
- How to prevent blind AI usage in the backend team
5. Submission Requirements
| Requirement | Detail |
|---|---|
| Format | |
| Length | Under 6 pages |
| AI Declaration | Mandatory — included in submission |
6. Domain Modules (Legacy Monolith)
┌─────────────────────────────────────┐
│ Legacy .NET Monolith │
├──────────┬──────────┬───────────────┤
│ Travel │ Event │ Payment │
│ Booking │ Mgmt │ Processing │
├──────────┴──────────┴───────────────┤
│ Operational Reporting │
├──────────────────────────────────────┤
│ Monolithic Database │
└──────────────────────────────────────┘
7. Key Questions to Address
- How to decompose the monolith into bounded contexts with only 5 engineers?
- How to migrate 40K users with zero downtime over 9 months?
- How to freeze payment flow in Phase 1 while modernizing other modules?
- How to ensure backward compatibility between legacy and new services during transition?
- What to sacrifice given the tight constraints (team size, timeline)?