Rocket.Chat is a production-grade, self-hosted team communication platform that provides real-time messaging, voice/video conferencing, omnichannel customer support (livechat), federation (Matrix), and an extensible app marketplace. The system is architected as a monorepo with a Meteor-based main application (apps/meteor) serving both the client (React with Fuselage UI) and server (Meteor methods, REST APIs via Hono, and microservices for enterprise features). Enterprise services (e.g., account, presence, authorization, DDP streamer) are implemented as separate polka-based microservices and gated by a license module. The client leverages React, TanStack Query, Zustand, and a rich component library (packages/ui-client). Data flows primarily through MongoDB (via typed model layers) with real-time updates pushed over DDP/WebSockets. File uploads use S3 or GridFS. Federation is achieved via Matrix protocol integration. The apps engine (packages/apps-engine) allows third-party apps to hook into message, room, and user events through a bridge pattern. The codebase includes extensive unit tests (Jest, Mocha), integration tests, Playwright e2e tests, and Storybook with a11y checks. External dependencies include MongoDB, Meteor, React, i18next, and a large set of npm packages managed by Yarn workspaces. The repository is actively maintained with frequent commits, changesets for versioning, and CI/CD pipelines.