Kommu

The Challenge

A community-focused startup needed a platform combining live video conferencing, instant messaging, event scheduling, and a complex permission system — essentially a modern alternative to Slack and Discord with built-in video rooms. The technical challenge was real-time state synchronization across hundreds of concurrent users with sub-second latency, while maintaining a permission model that operates at organization, channel, and room levels.

Discovery Phase

We mapped the permission model first — this was the architectural foundation everything else depended on. We identified 5 permission levels (owner, admin, moderator, member, guest) across 3 scopes (organization, channel, room). We then documented every real-time interaction: message sending, typing indicators, presence status, video room join/leave, and screen sharing. The critical constraint was that every state change needed to propagate to all connected clients within 200ms.

Our Solution

We chose Convex for real-time data synchronization — its reactive query model means UI components automatically re-render when underlying data changes, eliminating manual WebSocket management. LiveKit handles the video infrastructure with SFU (Selective Forwarding Unit) architecture for low-latency multi-party video. Clerk provides authentication with organization management, and we built a custom permission middleware that checks access at every API endpoint.

Architecture

The application uses a reactive architecture where every database query is a real-time subscription. When a user sends a message, all clients viewing that channel see it instantly through Convex reactive queries — no polling, no manual WebSocket management. The video layer is decoupled from the messaging layer, allowing independent scaling. LiveKit rooms are created on-demand and destroyed when empty, optimizing infrastructure costs.