Back to School Work
End-to-End System Pipeline & Data Flow
Delegation Request
Express API Gateway
Route Integrity Check
PostgreSQL (Sequelize)
Socket.io Real-Time Sync

Individual Engineering Contributions (Xin Ying)

1. Programme & Route Architecture Management

Architected and implemented the core backend services managing multi-day overseas business delegations and transport route allocation.

  • Built atomic programme and route creation flows ensuring each overseas delegation trip is deployed with designated route topologies (e.g., Coach A, Coach B).
  • Enforced strict single-route participant integrity rules in database models and controllers to prevent conflicting delegate bus assignments.
  • Engineered REST endpoints supporting programme status lifecycles (draft, active, completed) and batch delegate associations.
2. Real-Time Attendance Engine & SQL Bug Resolution

Developed the attendance tracking and live reporting engine, resolving critical database cross-join bugs through low-level SQL profiling.

  • Engineered manual and automated attendance marking controllers maintaining real-time present vs. missing participant counts.
  • Critical SQL Bug Fix: Discovered a latent cross-programme double-counting bug in the attendance summary query where missing rm.programme_id = ar.programme_id constraints caused delegates attending multiple programmes to be counted twice on shared routes; refactored subqueries in db.cjs to guarantee mathematical integrity.
  • Built ready-to-depart safety toggle APIs allowing trip managers to confirm vehicle readiness before proceeding between event stops.
-- Fixed attendance subquery preventing cross-programme double-counting anomaly SELECT r.id, r.route_name, COUNT(DISTINCT ar.user_id) AS total_assigned, COUNT(DISTINCT CASE WHEN a.status = 'present' THEN a.user_id END) AS total_present FROM routes r JOIN route_members rm ON rm.route_id = r.id AND rm.programme_id = :programme_id LEFT JOIN attendance a ON a.user_id = rm.user_id AND a.programme_id = :programme_id GROUP BY r.id, r.route_name;
3. Comprehensive 34-Endpoint Test Suite

Authored a fully independent, zero-dependency Node.js test runner in tests/xinying/ validating all endpoints against a live PostgreSQL instance.

  • Implemented dynamic test fixture setup creating isolated programmes and route instances per test run to ensure strict test idempotency without leftover data pollution.
  • Authored 34 rigorous endpoint tests covering programmes, routes, delegate associations, attendance tracking, and departure validation with a 100% pass rate.
  • Diagnosed and patched controller catch-guard mismatches (fixing unhandled 500 exceptions into structured 400 Bad Request responses).
4. AI System Design, Schemas & Chat-Log Transcripts

Authored complete system specifications, database entity-relationship models, and transparent AI-assisted development logs.

  • Produced 14 comprehensive use cases (docs/xinying/use-cases.md) defining Admin/Trip Manager and Staff/Secretariat interaction workflows.
  • Documented complete API specifications and database schemas with Mermaid ER diagrams across 7 relational tables.
  • Maintained structured AI development logs (ai/xinying/ai-logs/) capturing prompt iterations, scope boundary decisions, and algorithmic reflections.