Realtime sync
Realtime sync is the pattern where every connected client receives updates within milliseconds of a database change — without polling — via WebSockets, server-sent events, or similar live-channel mechanisms.
Realtime sync underlies multiplayer apps, collaborative tools, live chat, and notifications. By 2026 Convex makes every query reactive by default; Supabase ships realtime channels backed by Postgres logical replication; Firebase pioneered the pattern; Liveblocks specialises in presence + collaboration primitives. The hard problems: ordering, conflict resolution, scale (broadcasting to many clients), and authorization (which clients see which updates). Modern frameworks handle ordering via vector clocks or CRDTs and authorization via RLS rules tied to the realtime channel.
When to use realtime sync
- Collaborative apps (docs, design tools, dashboards).
- Chat and messaging.
- Live dashboards and notifications.
Common mistakes
- Polling instead of realtime — wastes resources at scale.
- Forgetting to scope realtime by user / org — security via RLS or channel auth is non-negotiable.
FAQ
What is realtime sync?
Realtime sync is the pattern where every connected client receives updates within milliseconds of a database change — without polling — via WebSockets, server-sent events, or similar live-channel mechanisms.
When should I use realtime sync?
Collaborative apps (docs, design tools, dashboards). Chat and messaging. Live dashboards and notifications.
What are the most common mistakes with realtime sync?
Polling instead of realtime — wastes resources at scale. Forgetting to scope realtime by user / org — security via RLS or channel auth is non-negotiable.
Related terms
- Serverless database — A serverless database scales compute and storage independently and bills based on actual use — no fixed instance provisioning — typical of Neon, PlanetScale, Supabase, Convex in 2026.
Last updated: 2026-06-01. Raw markdown: https://promtable.com/glossary/realtime-sync.md.