A full-stack business platform that connects modern web workflows with a long-running legacy insurance system without replacing the existing desktop operation.
My role
Full-stack product development & system architecture
Stack
Angular 17 · NestJS · gRPC · Redis · PostgreSQL · SQL Server · LINE LIFF · Docker
The problem
The business needed a web platform for staff operations and customer self-service, but its existing desktop application and SQL Server data could not simply be removed or rewritten. The challenge was to add modern workflows while keeping the legacy system operating normally.
What I built
I built a hybrid platform with Angular Web and LINE LIFF clients, a NestJS API Gateway, JWT + Redis session handling, and dedicated backend services for customers, policy/tax, LIFF, documents, notifications, and legacy SQL Server access. New application state is persisted through the PostgreSQL service into Neon PostgreSQL, while the legacy service reads the existing SQL Server source of truth without replacing the Delphi Desktop application.
My contributions
Designed and implemented hybrid data access between the legacy SQL Server system and new PostgreSQL workflows.
Built backend services and gRPC communication across the platform.
Implemented customer and vehicle search workflows, including license-plate and province matching with regression tests.
Built staff and customer workflows across the web platform and LINE LIFF.
Implemented dashboards, insurance/tax workflows, documents, notifications, and branch-aware operations.
Added health checks, smoke tests, deployment configuration, and security controls for production use.
Architecture
Key technical decisions
Keep legacy writes untouched
The existing desktop application continues its normal SQL Server writes and updates.
Separate old and new data paths
Legacy information is read through the bridge, while new web workflows use PostgreSQL.
Use gRPC between services
Internal service-to-service communication stays explicit and structured as the platform grows.
Keep the gateway as the API boundary
The frontend and LINE LIFF clients communicate with the NestJS API Gateway, which provides the REST entry point to the backend services.
Challenges & solutions
Legacy system integration
The existing desktop application and SQL Server database were still part of daily operations. I introduced a legacy bridge so the new platform could read existing data without forcing a full rewrite or migration.
Hybrid data flow
Some information remained in SQL Server while new workflows used PostgreSQL. I kept the data paths explicit and separated, then composed the required data at the application layer.
Search across systems
Customer and vehicle searches had to work with legacy records and new data. I implemented hybrid search behavior and added regression tests around license-plate and province matching.
Production operations
The platform needed more than feature development, so I added health checks, smoke tests, deployment configuration, and security controls to make the system easier to operate safely.
Engineering work
Hybrid customer and vehicle search across legacy SQL Server and new PostgreSQL data.
License-plate and province matching with regression tests for search behavior.
Customer and staff workflows through the web platform and LINE LIFF.
Dashboards, insurance/tax workflows, documents, notifications, and branch-aware operations.
Production-oriented health checks, smoke tests, deployment configuration, and security controls.
Result
The platform gives staff a modern web workspace and gives customers self-service experiences through Web and LINE, while the existing desktop operation and SQL Server data remain usable. The result is a controlled path from legacy infrastructure to modern services without requiring an all-at-once migration.
