Best practices for choosing a Time Series ID

This article covers the Azure Time Series Insights Preview partition key, the Time Series ID, and best practices for choosing one.

Choose a Time Series ID

Choosing a Time Series ID is like choosing a partition key for a database. It's an important decision that should be made at design time. You can't update an existing Time Series Insights Preview environment to use a different Time Series ID. In other words, when an environment is created with a Time Series ID, the policy is an immutable property that can't be changed.


The Time Series ID is case-sensitive and immutable (it can't be changed after it is set).

With that in mind, selecting the appropriate Time Series ID is critical. When you select a Time Series ID, consider following these best practices:

  • Pick a property name that has a wide range of values and has even access patterns. It’s a best practice to have a partition key with many distinct values (for example, hundreds or thousands). For many customers, this will be something like the DeviceID or SensorID in your JSON.
  • The Time Series ID should be unique at the leaf node level of your Time Series Model.
  • A Time Series ID property name character string can have up to 128 characters, and Time Series ID property values can have up to 1024 characters.
  • If some unique Time Series ID property values are missing, they are treated as null values, which take part in the uniqueness constraint.

Additionally, you can select up to three (3) key properties as your Time Series ID.


Your three (3) key properties must be strings.

The following scenarios describe selecting more than one key property as your Time Series ID:

Scenario one

  • You have legacy fleets of assets, each with a unique key.
  • For example, one fleet is uniquely identified by the property deviceId and another where the unique property is objectId. Neither fleet contains the other fleet’s unique property. In this example, you would select two keys, deviceId and objectId, as unique keys.
  • We accept null values, and the lack of a property’s presence in the event payload counts as a null value. This is also the appropriate way to handle sending data to two different event sources where the data in each event source has a unique Time Series ID.

Scenario two

  • You require multiple properties to be unique within the same fleet of assets.
  • For example, let’s say you're a smart building manufacturer and deploy sensors in every room. In each room, you typically have the same values for sensorId, such as sensor1, sensor2, and sensor3.
  • Additionally, your building has overlapping floor and room numbers across sites in the property flrRm, which have values such as 1a, 2b, 3a, and so on.
  • Finally, you have a property, location, which contains values such as Redmond, Barcelona, and Tokyo. To create uniqueness, you would designate the following three properties as your Time Series ID keys: sensorId, flrRm, and location.

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