Large-Scale Platform Migration

The Challenge

The existing platform was built on an aging technology stack that made feature development slow, testing unreliable, and performance inconsistent. With over 100,000 active users depending on the product daily, a full rewrite was too risky — but staying put meant falling further behind.

The goal: incrementally migrate to React without disrupting the user experience or slowing down feature delivery.

The Approach

I designed a strangler-fig migration strategy that allowed legacy and modern code to coexist. Key architectural decisions included:

• Module federation for shared dependencies between old and new surfaces
• Redux RTK as the state management layer, providing predictable data flow across migrated and legacy sections
• Feature flags to control rollout granularity — page by page, cohort by cohort
• Comprehensive testing with Jest and React Testing Library to catch regressions before they reached users

Each phase was scoped to a functional domain (authentication, dashboard, settings), validated in staging with real traffic patterns, and rolled out with monitoring dashboards in place.

Execution

The migration spanned 18 months across multiple feature teams. I served as the technical lead for frontend architecture, responsible for:

• Defining the component library and shared patterns that all teams followed
• Reviewing cross-team PRs to ensure consistency and quality
• Pairing with backend engineers on API contract changes required by the new frontend
• Running weekly architecture syncs to surface blockers early

Results

The migration delivered measurable improvements across performance, developer velocity, and user experience:

• 40% reduction in page load times through code splitting, lazy loading, and optimized bundling
• 3x faster feature development once teams were building on the new stack
• Zero critical regressions during the phased rollout, validated by automated smoke tests and real-user monitoring
• 5+ feature teams adopted the component architecture, creating consistency across the product