Modernizing a Production Frontend: 10x Faster Builds in 2 Weeks

In two weeks, we transformed our frontend development experience: developers went from waiting 30-60 seconds for the dev server to start, to just 2-5 seconds. Hot Module Replacement dropped from 2-3 seconds to under 100 milliseconds. What used to frustrate our team daily became instant, seamless, and delightful.

This is the story of how we migrated a production React application from Create React App to Vite, upgraded to React 18, and eliminated our monorepo complexity—all while maintaining zero downtime and zero production incidents. Through 22 commits touching over 2,000 files, we executed a systematic 5-phase migration that any team can replicate.

The Challenge: When Developer Experience Breaks Down

Our grow-frontend application had grown organically over years. What started as a simple Create React App had evolved into a complex monorepo managed by Turborepo, with 5+ package.json files, multiple workspace packages, and inter-dependencies that made every change feel like navigating a maze.

The pain points were becoming impossible to ignore:

Development Speed:

Cold start: 30-60 seconds to see your first change
HMR updates: 2-3 seconds per save (often requiring full reload)
Full reload: 10-15 seconds when HMR failed
Building for production: 2-3 minutes per build

Developer Frustration: Every code change meant waiting. Make a CSS tweak? Wait 2 seconds. Fix a typo? Wait 2 seconds. Over the course of a day with 100+ saves, that’s 3+ minutes of pure waiting. For a team of 10 developers, that’s 30+ minutes lost daily to build tooling—260 hours per year.

Architectural Complexity: Our monorepo structure created more problems than it solved. Five separate package.json files meant dependency version conflicts. Turborepo orchestration added build pipeline overhead. Workspace hoisting caused mysterious import resolution bugs. New developers needed hours just to understand the project structure.

Technical Debt: We were stuck on React 17.0.2, missing out on React 18’s concurrent features and automatic batching. Our test suite ran on Jest, which didn’t integrate well with modern ESM tooling. TypeScript compilation was slow. The entire stack felt outdated.

The business impact was clear: slower feature velocity, frustrated developers, longer onboarding times, and difficulty attracting talent who wanted to work with modern tooling.

The Stakes: Why We Couldn’t Afford to Fail

This wasn’t an academic exercise. We had an active product with real customers, ongoing feature development, and a release schedule to maintain. The migration had to happen without disrupting the business.

The risk factors were substantial:

Scale: 2,000+ files in an active codebase
Timing: We couldn’t afford multi-week feature freezes
Safety: Any production incidents would impact customer trust
Team: Migration had to be smooth for all developers

We needed a methodical approach that minimized risk while delivering maximum impact.

The Approach: A 5-Phase Migration Framework

Rather than attempting a “big bang” rewrite, we designed a phased approach where each phase delivered value and reduced risk for the next. This methodology is replicable for any team facing similar challenges.

Phase 1: Module Consolidation (December 10-15)

Goal: Reduce complexity and eliminate unused infrastructure before making major changes.

We started by cleaning house. Over five days, we:

Removed 204+ Storybook files across the entire codebase. Storybook had fallen out of use—it added build overhead without providing value. The team had moved to writing component tests instead, so we eliminated the dead weight.
Migrated the proposal-builder module from a standalone package into the main application. This eliminated cross-package imports and simplified our dependency graph. We updated 51 external import references, fixed 17 test files, and consolidated dependencies.
Deprecated PartnerAlign integration, removing conditional logic and UI indicators for a platform that was being sunset. Every line of code removed is a line we don’t have to maintain.

Key Lesson: Start any migration by removing what you don’t need. We cut hundreds of files before changing any build tooling, which made subsequent phases simpler and less risky. Complexity is your enemy—eliminate it first.

Phase 2: Flat Structure Migration (December 16-17)

Goal: Simplify architecture by eliminating monorepo complexity.

The monorepo structure had outlived its usefulness. We made the strategic decision to consolidate everything into a single application with a flat structure.

Over two days, we:

Consolidated 5+ package.json files into one. No more workspace configuration, no more inter-package dependencies, no more version conflicts.
Updated 200+ import paths from workspace package imports (@zomentum/ui-components) to local imports (@/V2Components/UI/atoms/ZButton). We configured TypeScript path aliases for clean imports and updated our build tooling accordingly.
Integrated all modules directly into src/: ProposalBuilder, Onboarding, and SalesActivity all became first-class directories in the main application.
Simplified CI/CD pipelines by removing Turborepo caching and workspace-specific build steps. Our GitHub Actions workflows became straightforward: install, lint, test, build.

Key Lesson: Sometimes the best architecture is the simplest one. Our monorepo added overhead without delivering its intended benefits (code sharing, independent versioning). The flat structure made everything clearer and faster. Simplify your architecture before changing your tools—it makes the tool migration dramatically easier.

Phase 3: Vite Build System Migration (December 17-19)

Goal: Replace Create React App and CRACO with Vite for 10x build performance.

This was the most technically challenging phase. Over three days, we:

Build System Replacement: We ripped out react-scripts, CRACO, and Webpack entirely. In their place, we configured Vite 5.0.12 with ESBuild for transpilation and Rollup for bundling. The configuration focused on:

Manual vendor chunking for optimal caching (React, Redux, Ant Design, Uppy, Charts)
Asset organization (images, fonts, JavaScript)
Multi-environment builds (development, staging, canary, production)
Bundle size limits and warnings

Node.js Polyfills: One of our dependencies (getstream) expected Node.js APIs like Buffer and process in the browser. Vite doesn’t polyfill these automatically like Webpack does. We implemented a comprehensive polyfill system that provides Buffer, process, and util globally without breaking modern ESM patterns.

Test Framework Migration: We migrated from Jest to Vitest, updating test patterns, mocking strategies, and setup files. Vitest’s native ESM support and Vite integration meant faster test execution and better developer experience. We configured jsdom environment, coverage reporting, and junit output for CI/CD integration.

SVG Import Changes: Create React App used { ReactComponent as Icon } imports; Vite uses different patterns. We updated 40+ SVG imports across the codebase and configured the SVGR plugin for React component generation.

Key Lesson: Build system migrations are the hardest part of any modernization. Tackle them separately from framework upgrades. The polyfill challenge taught us to audit third-party dependencies early—Node.js API expectations in browser code are more common than you’d expect.

Phase 4: React Upgrade (December 20)

Goal: Upgrade to React 18 to access concurrent features and modern APIs.

With a stable build system in place, the React upgrade was straightforward. In one day, we:

Upgraded React 17.0.2 → 18.3.1 and migrated the entry point from ReactDOM.render() to createRoot().render(). This unlocked React 18’s automatic batching and prepared us for concurrent features like useTransition and Suspense improvements.
Updated 13 CKEditor plugins that dynamically rendered React components. Each plugin needed proper root tracking with cleanup patterns to prevent memory leaks. We implemented a pattern using Map to track roots and unmount() calls in destroy methods.
Migrated modal and portal systems to use createRoot with proper cleanup. Our notification system, media preview modals, and onboarding highlight masks all got the React 18 treatment.

Key Lesson: Framework upgrades are much easier after your build system is modernized. The React 18 migration would have been significantly harder with Webpack and CRA. Modern build tools make framework upgrades less risky.

Phase 5: Cleanup & Configuration (December 20-24)

Goal: Ensure long-term maintainability through quality gates and cleanup.

The final phase focused on polish and sustainability. Over four days, we:

Fixed 42 TypeScript errors that surfaced post-migration: unused declarations, missing type definitions, and import resolution issues. We enforced strict mode and configured production-specific type checking with noUnusedLocals and noUnusedParameters.
Removed deprecated integrations like Beamer (product notification service) that were no longer in use.
Restored and fixed git hooks: pre-commit linting with lint-staged, pre-push type checking, and commit message validation with commitlint. These quality gates prevent regressions and maintain code quality automatically.
Validated all 8 environment configurations to ensure builds worked correctly for local, development, staging, canary, and production environments.

Key Lesson: Quality gates aren’t optional—they’re essential for maintaining the improvements you’ve achieved. Without automated checks, technical debt creeps back in. Git hooks are your first line of defense.

Key Challenges: Problem-Solving in Action

Every migration hits unexpected challenges. Here’s how we solved ours:

Challenge 1: Node.js Polyfilling for Browser Compatibility

The Problem: The getstream package (4.5.4) assumed Node.js APIs would be available in the browser—specifically Buffer, process, and util. Vite doesn’t automatically polyfill these like Webpack does. Build errors appeared immediately: Buffer is not defined, process is not defined.

Our Solution: We created a comprehensive polyfill module that provides these APIs globally before application initialization. We configured Vite to alias these packages to their browser-compatible versions and included them in dependency optimization. The polyfills load once at startup and provide seamless compatibility for all libraries expecting Node.js APIs.

Impact: Zero changes to application code or third-party libraries. The migration proceeded without needing to replace or fork dependencies.

Challenge 2: TypeScript Error Avalanche

The Problem: Post-migration, 40+ TypeScript errors appeared due to changed module resolution, stricter type checking, and missing type definitions for new patterns (especially SVG imports).

Our Solution: We created comprehensive type definitions for SVG imports supporting multiple patterns (*.svg, *.svg?react, *.svg?url). We completed interfaces with missing optional properties. We fixed path aliases in tsconfig.json to match Vite’s resolution. We systematically worked through each error category rather than rushing.

Impact: Strict type safety maintained throughout the migration. TypeScript caught real issues that could have become runtime bugs.

Challenge 3: CKEditor Plugin Memory Leaks

The Problem: Thirteen CKEditor plugins dynamically rendered React components using the deprecated ReactDOM.render() API. Migrating to React 18’s createRoot() required proper lifecycle management—roots must be explicitly unmounted to prevent memory leaks.

Our Solution: We implemented a pattern where each plugin maintains a Map of containers to roots. On initialization, we create roots and track them. On destroy, we iterate through all roots, unmount them, and clear the map. This ensures proper cleanup when plugins are removed or editors are destroyed.

Impact: React 18 compliant with zero memory leaks. Our application remains performant even with heavy document editing sessions.

Challenge 4: Memory Issues During Production Builds

The Problem: Production builds failed with “JavaScript heap out of memory” errors. Our bundle size and complexity exceeded Node.js’s default heap allocation.

Our Solution: We configured all build scripts with NODE_OPTIONS='--max-old-space-size=8192' to allocate 8GB of heap. We also optimized chunk sizes and implemented bundle size warnings to prevent future growth.

Impact: Reliable production builds that complete in 30-60 seconds without memory errors. Build process is robust and predictable.

Results: Quantifying the Business Impact

The migration delivered measurable improvements across every metric that matters:

Developer Experience Improvements

Dev Startup: 30-60s → 2-5s (10-12x faster)
HMR Updates: 1-3s → <100ms (20-30x faster)
Full Reload: 10-15s → 1-2s (7-10x faster)
Production Build: 2-3 min → 30-60s (3-4x faster)
Test Execution: 15-30s → 5-10s (2-3x faster)
Type Checking: 20-30s → 10-15s (2x faster)

Team Productivity Gains

Our analysis shows significant time savings:

Per developer per day: 6+ minutes saved (based on 100 code changes)
Team of 10 developers: 1 hour per day, 5 hours per week
Annual productivity gain: 260 hours (equivalent to 1.5 months of developer time)

Technical Foundation

Beyond raw performance, we achieved:

Modern React 18 with concurrent features ready for use (useTransition, Suspense improvements)
Simplified architecture from 5+ configuration files to 1, eliminating monorepo complexity
Improved code quality with strict TypeScript, comprehensive linting, and automated quality gates
Better testing infrastructure with Vitest’s native ESM support and improved developer experience

Long-term Benefits

The migration sets us up for future success:

Foundation for continued modernization (React 19, TypeScript 5, Vite 6)
Easier onboarding—new developers can start contributing faster with simpler architecture
Better IDE performance with straightforward import resolution
Reduced maintenance burden with modern, actively maintained tooling
Competitive advantage in recruiting—developers want to work with modern stacks

Lessons Learned: Wisdom for Other Teams

If your team is considering a similar migration, here’s what we learned:

Phase migrations incrementally. Our 5-phase approach minimized risk and delivered value at each stage. Big bang rewrites fail—incremental migrations succeed.
Clean up first, migrate second. We removed 204 files before changing any build tooling. Every line of code you don’t migrate is a line that can’t break.
Simplify architecture before changing tools. Flattening our structure made the Vite migration dramatically easier. If your architecture is complex, simplify it first.
Test infrastructure early and often. Each phase was validated before moving to the next. Automated testing and quality gates caught issues before they reached production.
Plan for polyfills and compatibility. Browser compatibility with Node.js APIs is non-trivial. Audit your dependencies for Node.js API usage and plan accordingly.
Document as you go, not after. We maintained comprehensive documentation throughout the migration. This helped team communication and created a reusable playbook.
Quality gates are non-negotiable. Git hooks, CI/CD checks, and automated linting prevent regressions. Without them, technical debt creeps back immediately.
Communication keeps teams aligned. Regular updates, clear milestones, and transparent planning minimized disruption and maintained team buy-in.

Conclusion: A Methodology, Not Just a Migration

This wasn’t just about switching from Webpack to Vite or upgrading React versions. It was about systematically improving our technical foundation while managing risk and maintaining business continuity.

The 5-phase approach we developed is replicable:

Phase 1: Reduce complexity
Phase 2: Simplify architecture
Phase 3: Modernize build system
Phase 4: Upgrade framework
Phase 5: Establish quality gates

Each phase builds on the previous one, delivering value and reducing risk incrementally. This methodology can be applied to any frontend modernization effort, regardless of your specific technology choices.

The results speak for themselves: 10x faster builds, instant HMR, improved developer experience, and a technical foundation ready for the future. Most importantly, we achieved this in two weeks with zero downtime and zero production incidents.

If your team is facing similar challenges with legacy build systems, outdated frameworks, or architectural complexity, the path forward is clear. Start with reducing complexity, simplify your architecture, then tackle your build system and framework upgrades systematically.

The future of frontend development is fast, and your team deserves tooling that doesn’t slow them down.

Have a similar modernization challenge? Let’s talk about your migration strategy. I’m always interested in discussing large-scale technical transformations and sharing lessons learned from the trenches.