Live Queries

LiveQuery runs a query and pushes updates whenever the underlying data changes. Great for dashboards and feeds.

Create a live query

import { Hub, LiveQuery } from "@mountsqli/realtime";

const hub = new Hub();
const live = new LiveQuery(hub, db.from(orders).where("status", "=", "open"));

const unsub = live.subscribe((change) => {
  console.log("orders changed:", change);
});

await live.start();

How it updates

When a write touches a table the query depends on, the Hub notifies the LiveQuery, which re-runs and publishes a LiveChange diff.

type LiveChange<T> = {
  type: "insert" | "update" | "delete";
  row: T;
  snapshot: T[];
};

Stop listening

unsub.unsubscribe(); // stops the live query

Real-world example

A live orders board:

const live = new LiveQuery(hub, db.from(orders).orderBy("createdAt", "desc"));
live.subscribe((change) => renderBoard(change.snapshot));
await live.start();

Best practices

• Scope live queries narrowly (filter + limit) — they re-run on writes.
• Unsubscribe on unmount to free the subscription.
• Pair with PresenceChannel for collaborative views.

Common mistakes

• Live-querying an unfiltered, huge table — every write re-scans it.
• Forgetting start() — no updates arrive.

Related

• Presence — who’s viewing.
• Cache — pair with query caching for read scaling.