> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cognite.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Data point subscriptions

> Subscribe to changes in time series data points in Cognite Data Fusion (CDF).

<Info>
  **Works with both data modeling and asset-centric projects.**

  You can reference time series using `instanceIds` (DM) or `timeSeriesIds` (asset-centric) when creating subscriptions.
</Info>

Data point subscriptions let you listen for changes to time series data points. Instead of polling for updates, you create a subscription that tracks new or changed data points across one or more time series.

## What you can do

* **Create subscriptions** — Register an interest in one or more time series.
* **Retrieve incremental updates** — Fetch only the data points that have changed since your last query.
* **Build real-time pipelines** — Use subscriptions as the foundation for streaming or event-driven data processing.

## Creating subscriptions

Subscriptions support two ways to specify which time series to track:

| Project type               | Parameter       | Description                                                         |
| -------------------------- | --------------- | ------------------------------------------------------------------- |
| **Data modeling**          | `instanceIds`   | Array of `{ space, externalId }` objects identifying DM time series |
| **Asset-centric (legacy)** | `timeSeriesIds` | Array of external IDs (strings)                                     |

You can also define subscriptions using a **filter** to dynamically track all time series matching certain criteria (for example, all numeric stepwise time series).

### Data modeling example

```json theme={"languages":{"custom":["/_languages/kuiper.json","../_languages/kuiper.json"]}}
{
  "items": [
    {
      "externalId": "my_subscription",
      "partitionCount": 1,
      "instanceIds": [
        { "space": "my_space", "externalId": "my_ts_1" },
        { "space": "my_space", "externalId": "my_ts_2" }
      ]
    }
  ]
}
```

### Asset-centric example

```json theme={"languages":{"custom":["/_languages/kuiper.json","../_languages/kuiper.json"]}}
{
  "items": [
    {
      "externalId": "my_subscription",
      "partitionCount": 1,
      "timeSeriesIds": ["my_ts_1", "my_ts_2"]
    }
  ]
}
```

## Key concepts

Subscriptions support incremental data retrieval, making them efficient for real-time data pipelines. You avoid repeatedly querying full time ranges when only new data has arrived.

<Info>
  Data point subscriptions are ideal for dashboards, alerting systems, and ETL pipelines that need to stay synchronized with the latest time series data.
</Info>