---
source_url: https://www.pubnub.com/docs/data-storage/structured-data/built-in-types
title: DataSync built-in types
updated_at: 2026-09-30T07:20:08.000Z
---

# DataSync built-in types

## Documentation index

To discover more PubNub resources:

1. Fetch [PubNub's llms.txt](https://www.pubnub.com/llms-full.txt) for a list of available pages in Markdown format.
2. Identify relevant URLs from that index.
3. Fetch the target pages.

Do not assume a path exists, always check the index first.

Users, channels, and memberships are DataSync's built-in classes. A user and a channel are entities. A membership is a relationship linking a channel to a user. Everything in the [Data model](https://www.pubnub.com/docs/data-storage/structured-data/data-model.md) applies to them: payloads, ETags, time-to-live (TTL), events, and access control.

## Users

A user is an entity of the built-in Global `User` entity class, which PubNub seeds at version 1. Creating a user requires only `entityClassVersion`. The `id` is optional, and DataSync generates one if you omit it.

The user endpoints are `Get users`, `Get user`, `Create user`, `Update user`, `Patch user`, and `Delete user`.

User fields:

| Field | Purpose |
| --- | --- |
| `id` | The user ID |
| `createdAt` | Creation timestamp |
| `updatedAt` | Last modification timestamp |
| `eTag` | Optimistic concurrency marker |
| `status` | A free-form application lifecycle string, 1 to 100 characters |
| `expiresAt` | Expiry timestamp. Inherits the Global class's 2,592,000 seconds (30 days) TTL by default |
| `entityClass` | The name of the entity class, `User` unless you've extended it |
| `entityClassVersion` | The version of the `User` class this instance pins to |
| `entityClassLevel` | Whether that class is `Global` or `SubKey` (keyset-level) |
| `payload` | Your application data |

The built-in `User` class declares two properties: `name` at `/payload/name` and `type` at `/payload/type`, both strings, nullable, fully filterable, and in the `__default__` projection. Any additional payload fields are stored as-is but aren't indexed.

The Global `User` class can't be changed. To add your own fields, define a class on your keyset that extends the Global `User` class through an `extends` reference. Your subclass inherits `name` and `type` automatically, and you only declare the fields you're adding. See [Class inheritance](https://www.pubnub.com/docs/data-storage/structured-data/schemas.md#class-inheritance).

A user's `id` is the same identifier as the UUID used elsewhere on PubNub for messaging and [Presence](https://www.pubnub.com/docs/presence/overview.md). They aren't the same stored record: DataSync keeps its own entity, separate from Presence and Pub/Sub state. A UUID works for messaging and Presence whether or not a matching entity exists in DataSync. Creating, updating, or deleting the entity has no effect on that UUID's ability to publish, subscribe, or appear in Presence.

## Channels

A channel is an entity of the built-in Global `Channel` entity class, with the same field shape as a user. A channel entity stores data about a channel your app uses for messaging, for example a display name or a category.

The channel endpoints are `Get channels`, `Get channel`, `Create channel`, `Update channel`, `Patch channel`, and `Delete channel`.

:::warning A channel entity is not a pub/sub channel
Creating a channel entity doesn't create or configure the underlying Pub/Sub channel, and a channel does not need an entity for messaging to work. The entity holds metadata. The Pub/Sub and Presence channel carries messages and subscribers. They share an ID but have separate lifecycles.
:::

## Memberships

A membership is a relationship of the built-in Global `Membership` relationship class, linking a channel and a user. The `Membership` class is many-to-many, so a user can belong to many channels and a channel can have many members.

The membership endpoints are `Get memberships`, `Get membership`, `Create membership`, `Update membership`, `Patch membership`, and `Delete membership`.

Membership fields, in addition to the standard system fields:

| Field | Purpose |
| --- | --- |
| `id` | The membership's own identifier |
| `channelId` | The linked channel's ID (entity A) |
| `userId` | The linked user's ID (entity B) |
| `relationshipClass` | Always `Membership`, set by DataSync |
| `relationshipClassVersion` | The version of the `Membership` class this instance pins to |
| `payload` | Association data, for example a role |

Creating a membership requires `channelId`, `userId`, and `relationshipClassVersion`. Both the channel and the user must already exist, or the request returns a `404`. Only one membership can exist for a given channel and user, so a duplicate returns a `409`.

Membership lists can be narrowed by `user_id`, by `channel_id`, or by both together, covering the two common questions: which channels a user belongs to, and who is a member of a channel. Refer to [Get memberships](https://www.pubnub.com/docs/sdks/rest-api/get-memberships.md).

Because the `Membership` class declares no properties and can't be extended, membership payload fields are never indexed. The built-in fields `id`, `createdAt`, `updatedAt`, and `status` are still filterable and sortable.

## Real-time updates

Creating, updating, or deleting a user, channel, or membership can publish a DataSync event, the same way any other entity or relationship can. Events are off by default and enabled per class version, per keyset, in the Admin Portal.

A create event for a user publishes on that user's ID channel. Update and delete events also publish on the ID channels of every entity the user is linked to by a relationship. A membership event publishes on both the linked channel's and the linked user's ID channels, never on the membership's own ID channel.

To watch a user's memberships appear and disappear, subscribe to the user's ID channel, not to any membership ID. Refer to [Events](https://www.pubnub.com/docs/data-storage/structured-data/events.md) for the full routing model.

[Access Manager](https://www.pubnub.com/docs/security/access-control/overview.md) tokens grant permissions on the same user and channel IDs you use here. Memberships are a separate `datasync:memberships` resource type, so granting access to a user or channel doesn't authorize creating, updating, or deleting memberships between them. Refer to [DataSync access control](https://www.pubnub.com/docs/data-storage/structured-data/access-control.md).

## Comparison with App Context

| App Context | DataSync |
| --- | --- |
| User metadata with top-level `name`, `email`, `profileUrl`, `externalId`, `custom` | User entity with all application data inside `payload` |
| Channel metadata | Channel entity with data in `payload` |
| Membership with custom data | Membership relationship with `payload` |
| Optional Access Manager | Access Manager required |
| Set/delete events (message type 2) | Create/update/delete events (message type 5) |

App Context keeps working, and there is no automatic migration of existing data to DataSync.

Last updated at: 2026-09-30T07:20:08.000Z