BigBlueButton is an open-source web conferencing system designed for online learning. It provides real-time audio/video, screen sharing, whiteboard, chat, polling, breakout rooms, and recording/playback. The architecture is distributed and polyglot: a Scala/Akka backend handles meeting logic and state via Redis pub/sub; a Java API layer exposes REST endpoints for meeting creation and recording management; a React frontend with GraphQL subscriptions enables real-time collaboration; Ruby workers process recordings; and a Go GraphQL middleware optimizes subscription delivery. The system integrates with FreeSWITCH for legacy voice and LiveKit for modern WebRTC audio. A plugin SDK allows third-party extensions via customizable UI areas and data consumption hooks. Despite a large feature set and active development, the codebase suffers from significant technical debt due to its multi-language nature, incomplete migrations (e.g., from Meteor to pure React), duplicated logic across frontend and backend, and outdated library versions. Reusable components include the Redis pub/sub framework, GraphQL subscription deduplication hooks, and an annotation export service.