E-Commerce Platform Redesign
Complete rebuild of a legacy e-commerce system serving 2M+ monthly users
Role: Lead Engineer & Architect
Context
The client's existing e-commerce platform was built on a monolithic PHP codebase from 2012. With 2 million monthly active users and growing, the system struggled with performance, maintenance, and feature velocity.
Problem
The legacy system faced several critical challenges:
- Page load times exceeded 5 seconds on mobile devices
- Mobile experience was poor, leading to high bounce rates
- Checkout conversion rate was declining month over month
- Development velocity had slowed to a crawl due to technical debt
- Technical debt made new features risky to implement
Approach
We decided on a phased migration strategy rather than a risky big-bang rewrite:
Phase 1: API-First Architecture
Built a new REST API with a GraphQL layer on top for flexible querying. This allowed the old and new frontends to coexist during migration.
Phase 2: Incremental Adoption
Migrated pages one at a time, starting with the highest-traffic pages. Used feature flags to gradually shift traffic to the new experience.
Phase 3: Performance Budget
Established a strict 2-second page load target. Every PR was tested against this budget, and violations blocked deployment.
Phase 4: Type Safety
Implemented full TypeScript coverage across the stack. Types were generated from the database schema to ensure consistency.
Phase 5: Modern Infrastructure
Deployed on Vercel with edge caching. Static pages were pre-rendered at build time, while dynamic content used ISR (Incremental Static Regeneration).
Technical Decisions
Why Next.js?
- Server-side rendering for SEO
- Static generation for performance
- API routes for backend logic
- Built-in image optimization
Why PostgreSQL + Redis?
PostgreSQL for transactional data, Redis for:
- Session storage
- Cart persistence
- Rate limiting
- Real-time inventory checks
Why Stripe?
- Excellent developer experience
- Built-in fraud protection
- Subscription support for future plans
Outcome
After 6 months of development:
- Page load times reduced to under 1.5s (70% improvement)
- Checkout conversion increased by 23%
- Mobile traffic grew 45% as experience improved
- Development velocity doubled with better tooling
- Zero downtime during the entire migration
Lessons Learned
The biggest challenge wasn't technical—it was managing stakeholder expectations during the migration. We learned the importance of:
Visible Progress
Weekly demos kept everyone aligned and excited. We celebrated each page migration as a milestone.
Data-Driven Decisions
A/B testing validated every major change. When stakeholders pushed back on design decisions, we let the data speak.
Rollback Plans
We tested every rollback scenario before deploying. This confidence allowed us to move faster.
What I'd Do Differently
If I were to do it again, I'd invest more time upfront in observability. We added comprehensive monitoring halfway through, which revealed bottlenecks we hadn't anticipated.
I'd also push harder for a design system earlier in the process. We ended up building components twice as the design evolved.