Case Study: High-Performance Next.js Platform Migration

Overview

I served as Lead Front End Engineer on a large-scale migration for a travel insurance company transitioning from a legacy Sitecore implementation to a modern, headless Next.js architecture powered by ButterCMS. The project focused on improving performance, accessibility, and frontend flexibility, while enabling content authors to continue building complex pages at scale.

Role: Lead Front End Engineer / Technical Architect

Stack: Next.js (App Router), React, ButterCMS

The Problem

The client’s existing Sitecore site had grown highly complex over time, with:

• Heavy CMS-driven page composition
• Over 1,000 blog posts and content pages
• Multiple page templates and layouts
• Poor performance and failing Core Web Vitals
• Limited architectural flexibility for the internal engineering team

Pages loaded slowly, interaction latency was high, and the existing architecture made it difficult to improve performance without major rework. The client wanted to move to a headless CMS approach that would give their engineering team control over frontend architecture while preserving robust CMS authoring capabilities.

Constraints & Requirements

• Migrate a large, content-heavy marketing site (~1,000 blog posts)
• Preserve flexible, author-driven page building
• Support multiple page types and layouts
• Improve Core Web Vitals and perceived performance
• Maintain SEO, accessibility, and content standards
• Balance server-side and client-side rendering intentionally
• Enable other developers to contribute within a consistent architecture

The Solution

Frontend Architecture & Rendering Strategy

I designed and implemented a Next.js application using the App Router, integrating ButterCMS as a headless content source. A key architectural decision was adopting a hybrid rendering strategy:

• Server-side rendering (SSR) for the majority of content to improve load time, SEO, and Core Web Vitals
• Client-side rendering (CSR) only for highly interactive components (e.g., accordions, sliders, stateful UI)

This approach ensured fast initial loads while keeping interactivity responsive and intentional.

As the lead engineer, I:

• Established the core Next.js architecture and project structure
• Led an architecture walkthrough and demo for the other developers before implementation began
• Reviewed code throughout the project, providing guidance on code quality, accessibility, and rendering tradeoffs

CMS-Driven Page Composition

To support non-technical content authors, I built:

• 30+ reusable, production-ready React components
• Custom templates for core page types (homepage, solution pages, landing pages, blog posts, blog listings)
• A dynamic routing system using the Next.js App Router that:
  • Generated pages based on CMS-defined URL paths
  • Mapped page types to appropriate layouts automatically
  • Allowed authors to create pages with custom URLs without engineering involvement

Each component was designed to balance:

• Stability (protecting layout, performance, and accessibility)
• Flexibility (layout variants, styling options, and content configuration)

Performance, SEO & UX Optimization

Performance was a primary focus throughout development. I emphasized:

• Careful separation of server-rendered and client-rendered components
• Image optimization and responsive image handling
• Minimizing unnecessary JavaScript and re-renders
• Ensuring that individual components remained lightweight so their combined usage would not degrade performance
• Adding skeleton loaders and loading indicators for client-rendered components to improve perceived performance

SEO and accessibility considerations were built into the architecture, along with clear guidelines for content authors to help maintain consistent structure, semantics, and performance as new content was added.

Outcome

• Successfully migrated a large Sitecore site to a Next.js + headless CMS architecture
• Improved Core Web Vitals from failing to passing, with Largest Contentful Paint ~2000ms
• Delivered a flexible CMS-driven frontend with 30+ reusable components
• Significantly improved perceived performance; the client reported the site “felt much faster”
• Received strong client feedback and was requested again for a subsequent project