SaaS Platform Rebuild: From 6s to 0.4s LCP
Complete platform rebuild using Astro + Preact Islands, cutting load times by 87% and doubling conversion rates.
Client: CloudMetrics (illustrative)
"RexBunny didn't just rebuild our site — they rebuilt our business. The performance gains translated directly to revenue."
— Illustrative clientSample quote shown for illustration; not attributed to a real named customer.
The Challenge
A representative SaaS client arrived with a monolithic React app that took 6.2 seconds to load on mobile. Their Lighthouse score was 34. Bounce rates were climbing. They needed a complete rethink, not a patch.
Our Approach
Architecture
We migrated from a single-page React application to Astro with Preact Islands. Content pages became static HTML (zero JavaScript). Interactive dashboards became isolated Preact components that load only when needed.
Performance Engineering
- Font optimization: Subset Inter to Latin characters only, preload critical fonts
- Image pipeline: Automatic WebP conversion, responsive srcsets, lazy loading
- Code splitting: Every page ships only the JavaScript it needs
- Edge deployment: Content served from 200+ edge locations globally
AI Search Optimization
- Added
llms.txtwith structured business information - Implemented
LocalBusinessandSoftwareApplicationschema - Configured
robots.txtto allow AI crawlers - Created citation-friendly content structure
Results
| Metric | Before | After | Change |
|---|---|---|---|
| Lighthouse | 34 | 98 | +188% |
| LCP | 6.2s | 0.4s | -93% |
| CLS | 0.22 | 0.01 | -95% |
| TBT | 1,200ms | 42ms | -97% |
| Bounce Rate | 68% | 31% | -54% |
| Conversion Rate | 2.1% | 4.1% | +96% |
The performance improvements also boosted AI visibility. In a representative case, the site moved from zero AI citations to being surfaced in ChatGPT responses for “cloud analytics platform” queries within 60 days — a new channel the client hadn’t reached before.
Related reading:
- Our Web Development Service — Lighthouse 95+ guaranteed
- How We Engineer Sub-Second Lighthouse Scores — Our technical blueprint
- What is GEO? — Why AI search matters for SaaS