Incrementally Migrating and Modernizing a Legacy HR Platform
After years of growth, the legacy HR platform was becoming slow and difficult to maintain. I led the migration to a modern tech stack, using an incremental approach (Strangler Fig Pattern) to ensure uninterrupted service while gradually modernizing features.
🧭 Context: The Legacy Challenge
The application was over 4+ years old, with many features added over time. The technical debt accumulated had made development slow and maintenance risky.
- Deteriorating Performance: Users experienced slow load times and janky interactions, impacting feature adoption and user trust.
- High Operational Cost: Running on traditional servers meant paying for idle capacity, leading to unnecessarily high hosting costs.
- Poor Developer UX: Lack of modern tooling, dependency management issues, and untyped JavaScript made the codebase difficult to work with and maintain.
- Downtime Risk: A full, sudden rewrite was not feasible due to the critical nature of the HR data and the need for 24/7 access.
🎯 Objective: Modernization and Cost Optimization
The objective was to revitalize the entire platform architecture, eliminating technical debt and establishing a foundation for future scalability and reliability.
- Lead the planning, design, and execution of the incremental migration.
- Migrate all core features to the new stack without service interruption.
- Improve performance, scalability, and maintainability.
- Achieve measurable cost savings by optimizing the infrastructure model.
- Deliver a significantly better user experience (UX) and a modern design.
⚙️ Solution: Incremental Serverless Migration
I spearheaded the migration using a strategic, feature-by-feature transition that leveraged the best of modern web and cloud architecture.
Key Technical & Strategy Highlights:
- Incremental Migration Strategy: New features were developed on the modern stack first. Existing features were gradually migrated, using routing to direct traffic away from the legacy app to the new component until the old platform was fully "strangled."
- Frontend Modernization: Switched to Next.js for hybrid rendering (SSR/ISR) and superior routing, TypeScript for code safety, and Tailwind CSS + shadcn/ui for rapid, modern, and accessible UI development.
- Serverless Backend: Migrated heavy backend logic from long-running servers to AWS API Gateway + Lambda + SQS, adopting a pay-per-use model for maximum cost efficiency and horizontal scalability.
- Infrastructure-as-Code (IaC): Used Terraform to define all backend services, ensuring repeatable, auditable, and easily modifiable infrastructure deployments.
- Secure Integrations: Preserved complex, secure workflows (e.g., Stripe Integration for payments) through carefully managed API contracts between the old and new systems.
✨ Results & Impact: Operational Excellence and Savings
The successful modernization delivered immediate, high-impact results across three critical areas: User Experience, Operational Costs, and Developer Velocity.
🚀 Performance & User Experience (UX)
| Metric | Impact | Key Driver |
|---|---|---|
| Average Page Load Time | 45% Faster | Next.js SSR/ISR, automatic code splitting, optimized bundles. |
| Design / Look & Feel | Major Upgrade | Implementation of a modern, responsive design system using Tailwind and shadcn/ui. |
| Site Responsiveness | Significantly Improved | Reduced client-side JavaScript bundle size and optimized component rendering. |
💰 Operational Cost & Scalability
| Metric | Impact | Key Driver |
|---|---|---|
| Monthly Infrastructure Cost | More than 50% Reduction | Full transition to AWS Serverless (Lambda, API Gateway), eliminating cost of idle server capacity. |
| Scalability | Near-Limitless | Pay-per-use, elastic scaling enabled instantaneous handling of high-traffic events without manual intervention. |
| Maintenance Overhead | Drastically Reduced | AWS managed server operations, OS patching, and security updates. |
🛠️ Developer Experience (DevX) & Code Quality
| Metric | Impact | Key Driver |
|---|---|---|
| Feature Development Speed | 50% Faster | Replaced legacy codebase with component-based Next.js and atomic styling (Tailwind CSS). |
| Code Reliability | Major Improvement | Adoption of TypeScript caught an estimated ~80% of common runtime errors during the build phase. |
| Onboarding Time | Reduced by 75% | Clear architecture, modern tooling, and type-safe code made new developers productive in days instead of weeks. |
This project successfully executed a complex technical migration while demonstrating clear ROI. The platform is now secure, highly performant, and equipped with a developer-friendly architecture that can support the company's growth for the next decade.