eCommerce Fashion Marketplace Platform — UK Multi-Brand Retailer

Headless Shopify Plus Architecture: Shopify Plus (enterprise tier): supports headless via Storefront API, multi-brand product management, wholesale/B2B pricing, and Shopify Payments. Headless frontend: Next.js App Router — ISR (Incremental Static Regeneration) for product pages (regenerated on stock change), Server Components for product listing (zero client-side JavaScript for SEO), and Client Components only for interactive elements (basket, wishlist, filters). CDN: Vercel Edge Network for global performance (UK edge — <50ms TTFB from UK). Multi-Brand Marketplace Architecture: 340 brand seller portals: Shopify Plus multi-location inventory (each brand = separate location), brand-specific product management portal (React admin), and commission calculation (% of GMV per brand per product category). Brand payout: Stripe Connect (marketplace payments — platform holds funds, transfers to brands on settlement schedule). UK GDPR: each brand is a data controller for their customer interactions — platform is joint controller. Inter-brand data sharing: prohibited — brand A cannot see brand B's sales data. PCI-DSS SAQ-A Migration from Magento: Magento 1: SAQ-D (most complex PCI tier) because Magento handled card data. Migration to Shopify Plus + Stripe Elements: SAQ-A (22 requirements). Migration risk: no payment data on legacy system to migrate (Stripe handles all card data). Customer accounts: email/address migrated from Magento — no payment data. PCI-DSS scope reduction: from 329 SAQ-D requirements to 22 SAQ-A requirements — 93% compliance reduction. Core Web Vitals and Mobile Conversion: Mobile conversion target: 18% (from 2.1% on Magento 1). LCP < 1.8s on mobile: Next.js Image optimisation (WebP + AVIF, lazy loading, priority prop for above-fold images), Cloudflare Images CDN, and font optimisation (next/font, self-hosted). FID/INP < 150ms: minimal client-side JavaScript (Server Components for 80% of page), React transitions for filter changes. CLS < 0.05: image aspect ratios preserved, skeleton screens for dynamic content. Real User Monitoring: Vercel Analytics + Sentry Performance.