PCByte is a complete e-commerce ecosystem for a technology store, architected across four independent projects. The backend is built on Medusa.js with Redis caching and custom modules for AWS S3 dual-bucket storage, PayPal payments, manual bank transfer, Meilisearch indexing, Odoo ERP synchronization, transactional emails via Resend, weight-based fulfillment, product attributes, media, and reviews. The Next.js 16 storefront uses React 19, next-intl, TanStack Query, Zustand, Jotai and ships with Redis-backed rate limiting, Google reCAPTCHA v3, honeypot fields, DOMPurify sanitization and a Strapi-powered headless CMS. The mobile app is built with Expo and React Native, using secure storage, biometric authentication and MMKV. Strapi (PostgreSQL + S3) powers editorial content. Quality is enforced through unit, integration and Playwright end-to-end tests on the backend and storefront, plus a Vitest suite on the frontend and Jest unit tests on mobile.