Real-time Sync

PRODUCTS

Keep devices and users in step. Channels carry messages between everyone using your app, and the client keeps your data working while the connection comes and goes.

Channels. Publish to a named channel and every subscriber gets the message, whichever key they use: chat, presence, live cursors, "this changed, reload it".
Offline queueing. Writes made without a connection are queued on the device and sent when it's back. Reads of the same key keep working from the local copy.
Optimistic updates. Show a change right away and let the client confirm it with the server, or roll it back if the server refuses it.
Sync events. One listener tells you when something was queued, pushed, confirmed or rolled back.

Channels are polled (every 3 seconds by default), and messages are kept for 3 days: use them for live updates, and the regular read and write calls for anything you need to keep. Anyone who knows a channel's name can use it, so give it a name that's hard to guess.

Read the docs Back to home

            
            
            
            
          

            1// load prefsdb.channels.v1.min.js after prefsdb.v1.min.js
2const db = await PrefsDB.getkey("my-app", words);
3const room = db.channel("my-app-room-42");
4 
5// every subscriber sees every message, oldest first
6const stop = room.subscribe((msg) => {
7  show(msg.sender, msg.value);
8});
9 
10await room.publish({ text: "hello" });
11 
12// later
13stop();

          

            1const db = await PrefsDB.getkey("my-app", words);
2 
3// offline? the write is queued on the device
4// and replayed when the connection comes back
5await db.key("draft").write(text);
6 
7// reads of that key are served from the local copy
8const draft = await db.key("draft").read();
9 
10PrefsDB.onSyncEvent((e) => {
11  if (e.phase === "pushed") markSaved(e.key);
12});

          

            1const db = await PrefsDB.getkey("my-app", words);
2 
3// apply locally now, confirm with the server after
4await db.key("likes")
5        .write(likes + 1, { optimistic: true });
6 
7PrefsDB.onSyncEvent((e) => {
8  if (e.phase === "optimistic-rollback") {
9    // the server refused it: the old value is back
10    render();
11  }
12});

          

            1# publish to a channel
2curl -s -X POST "https://prefsdb.com/api/v1/channel/publish/?channel=my-app-room-42" \
3  -H "X-Authorization: Token $KEY" -b cookies.txt \
4  -H "Content-Type: text/plain" --data "hello"
5 
6# fetch messages after cursor 0
7curl -s "https://prefsdb.com/api/v1/channel/poll/?channel=my-app-room-42&since=0" \
8  -H "X-Authorization: Token $KEY" -b cookies.txt
9 
10# => { "success": true, "cursor": "17",
11#      "messages": [{ "id": "17", "sender": "...", "value": "hello" }] }

          

1	// load prefsdb.channels.v1.min.js after prefsdb.v1.min.js
2	const db = await PrefsDB.getkey("my-app", words);
3	const room = db.channel("my-app-room-42");
4
5	// every subscriber sees every message, oldest first
6	const stop = room.subscribe((msg) => {
7	show(msg.sender, msg.value);
8	});
9
10	await room.publish({ text: "hello" });
11
12	// later
13	stop();

1	const db = await PrefsDB.getkey("my-app", words);
2
3	// offline? the write is queued on the device
4	// and replayed when the connection comes back
5	await db.key("draft").write(text);
6
7	// reads of that key are served from the local copy
8	const draft = await db.key("draft").read();
9
10	PrefsDB.onSyncEvent((e) => {
11	if (e.phase === "pushed") markSaved(e.key);
12	});

1	const db = await PrefsDB.getkey("my-app", words);
2
3	// apply locally now, confirm with the server after
4	await db.key("likes")
5	.write(likes + 1, { optimistic: true });
6
7	PrefsDB.onSyncEvent((e) => {
8	if (e.phase === "optimistic-rollback") {
9	// the server refused it: the old value is back
10	render();
11	}
12	});

1	# publish to a channel
2	curl -s -X POST "https://prefsdb.com/api/v1/channel/publish/?channel=my-app-room-42" \
3	-H "X-Authorization: Token $KEY" -b cookies.txt \
4	-H "Content-Type: text/plain" --data "hello"
5
6	# fetch messages after cursor 0
7	curl -s "https://prefsdb.com/api/v1/channel/poll/?channel=my-app-room-42&since=0" \
8	-H "X-Authorization: Token $KEY" -b cookies.txt
9
10	# => { "success": true, "cursor": "17",
11	# "messages": [{ "id": "17", "sender": "...", "value": "hello" }] }