DataSync event format reference

Showing JavaScript examples.

DataSync events are PubNub messages with message type 5. This distinguishes them from ordinary messages. Each event carries a versioned envelope with a metadata section and a data section.

Envelope schema

{
  "version": "1.0",
  "metadata": {
    "event": "create" | "update" | "delete",
    "source": "data-sync",
    "type": "user" | "channel" | "membership" | "entity" | "relationship",
    "className": "Product",
    "classLevel": "Global" | "SubKey",
    "classVersion": 1
  },
  "data": { ... }
}

Metadata fields

Field	Type	Description
version	string	Envelope version. Always 1.0 for DataSync events
metadata.event	string	create, update, or delete
metadata.source	string	Always data-sync
metadata.type	string	The object kind: user, channel, membership, entity, or relationship
metadata.className	string	The class name, for example Product or User. Read together with classLevel to distinguish a built-in class from a same-named keyset-level class
metadata.classLevel	string	Global (PubNub-owned) or SubKey (keyset-level)
metadata.classVersion	number	The class version the object pins to

metadata.type is derived from the Global class the class descends from, not from its name. A keyset-level class extending the built-in User reports type: "user" alongside its own className and classLevel: "SubKey". A keyset-level class merely named User that extends nothing reports type: "entity".

Data field shapes

For create and update events, data carries the object's current state, scoped to the projection for the channel it's delivered on:

Field	Present on
id	All object kinds
createdAt	All object kinds
updatedAt	All object kinds
expiresAt	All object kinds (omitted if not set)
eTag	All object kinds
status	All object kinds (omitted if not set or outside projection)
payload	All object kinds (omitted if empty or outside projection)
entityAId	Relationships only
entityBId	Relationships only
channelId	Memberships only
userId	Memberships only

For delete events, data is exactly { id, deletedAt } for every object kind alike. No payload or status is included.

Fields that have no value are omitted from data rather than sent as null. Read every field except id defensively.

Example events

Update event

{
  "version": "1.0",
  "metadata": {
    "event": "update",
    "source": "data-sync",
    "type": "entity",
    "className": "Product",
    "classLevel": "SubKey",
    "classVersion": 1
  },
  "data": {
    "id": "product-sneaker-42",
    "status": "active",
    "eTag": "a1b2c3",
    "createdAt": "2026-06-01T10:00:00Z",
    "updatedAt": "2026-07-03T09:15:00Z",
    "expiresAt": "2026-08-01T00:00:00Z",
    "payload": { "name": "Retro Sneaker", "price": 79.99, "stock": 12 }
  }
}

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Delete event

{
  "version": "1.0",
  "metadata": {
    "event": "delete",
    "source": "data-sync",
    "type": "entity",
    "className": "Product",
    "classLevel": "SubKey",
    "classVersion": 1
  },
  "data": {
    "id": "product-sneaker-42",
    "deletedAt": "2026-07-03T09:20:00Z"
  }
}

Membership create event

A membership event carries type: "membership" and names its sides channelId and userId:

{
  "version": "1.0",
  "metadata": {
    "event": "create",
    "source": "data-sync",
    "type": "membership",
    "className": "Membership",
    "classLevel": "Global",
    "classVersion": 1
  },
  "data": {
    "id": "membership-alice-sale",
    "status": "active",
    "eTag": "d4e5f6",
    "createdAt": "2026-07-03T09:15:00Z",
    "updatedAt": "2026-07-03T09:15:00Z",
    "expiresAt": "2026-08-01T00:00:00Z",
    "channelId": "channel-summer-sale",
    "userId": "user-alice",
    "payload": { "role": "viewer" }
  }
}

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A membership event never carries entityAId or entityBId. A relationship of your own carries those two fields instead and never channelId or userId.

How the event is received per SDK

• JavaScript
• C#

1subscription.onDataSync = (event) => {
2    const change = event.message
3    console.log(change.event, change.className, change.data.payload?.price)
4}

The JavaScript SDK flattens the wire envelope: metadata.event arrives as event.message.event, metadata.className as event.message.className, and so on. event.message.data is the raw data object.

Using the REST subscribe endpoint directly, the raw response carrying an event looks like:

1curl -N 'https://ps.pndsn.com/v2/subscribe/{subKey}/product-sneaker-42/0?tt=0&auth=<token>'

[
    [
        {
            "version": "1.0",
            "metadata": {
                "event": "update",
                "source": "data-sync",
                "type": "entity",
                "className": "Product",
                "classLevel": "SubKey",
                "classVersion": 1
            },
            "data": {
                "id": "product-sneaker-42",
                "status": "active",
                "eTag": "a1b2c3",
                "createdAt": "2026-06-01T10:00:00Z",
                "updatedAt": "2026-07-03T09:15:00Z",
                "expiresAt": "2026-08-01T00:00:00Z",
                "payload": { "name": "Retro Sneaker", "price": 79.99, "stock": 12 }
            }
        }
    ],
    "15467028383205111"
]

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Refer to Add DataSync listener (JavaScript) and Add DataSync listener (C#) for the full SDK field reference.

Comparison with App Context events

DataSync events use a different format from App Context events. Existing App Context event consumers are unaffected.

Aspect	App Context	DataSync
Message type	2	5
source	objects	data-sync
Verbs	set, delete	create, update, delete
Envelope version	2.0	1.0