Amey-Thakur Presence and awareness
Presence is what makes collaboration feel live: seeing a cursor move tells you not to edit that paragraph. It is also ephemeral, high frequency, and privacy sensitive, which makes it a different problem from document state.
Method
- Keep presence out of the persistent store. It is transient by nature, and writing cursor positions to a database is a load problem with no benefit.
- Throttle and interpolate. Send positions at a modest rate and smooth between them on the client, since users perceive continuity rather than sample rate.
- Expire presence rather than trusting disconnect. Clients vanish without saying goodbye, so a heartbeat with a timeout is what removes ghosts (see websockets-at-scale).
- Scale by room, and cap what is broadcast. Full presence for everyone in a large room is quadratic traffic; above a threshold show a count and a sample rather than every cursor.
- Make presence a deliberate disclosure. Being visibly present, and visibly idle, is information about a person. Offer invisible or view-only modes where the context warrants it (see data-minimization).
- Distinguish presence from permission. Seeing someone in a document is not the same as knowing what they may do, and the UI should not imply otherwise.
- Degrade gracefully. When the presence channel drops, the document must keep working; presence is an enhancement, never a dependency.
Boundaries
- Presence indicates attention approximately; typing indicators and idle states are inferred and often wrong.
- Showing identity in shared spaces has privacy implications in some contexts, particularly anonymous or public documents.
- High-frequency presence traffic can dominate costs at scale and deserves its own budget.