Medusa is a headless commerce platform built as a modular monorepo. It provides a comprehensive backend with REST APIs for admin and storefront operations, a React-based admin dashboard, a workflow engine for orchestrating business processes (orders, returns, claims, etc.), and a plugin system for extending functionality. The architecture is domain-driven: each commerce domain (cart, order, product, pricing, payment, fulfillment, inventory, tax, promotion, customer, region, etc.) is an independent module with its own models, migrations, services, and workflows. The admin dashboard is a React SPA using TanStack Query, react-hook-form, and a custom data grid with virtual cells and clipboard support. The platform relies on PostgreSQL (via MikroORM) and optionally Redis for caching and workflow execution. It includes a design system with SVG icons and UI components, a JS SDK for client-side integration, and extensive documentation sites built with Next.js. The monorepo also contains CLI tools for project scaffolding, code generation, and API reference generation.