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

# Primary Key

> Reference for the primary key structure used to uniquely identify summary and timeseries data records in the Junction data model.

## Summary types

Each summary is uniquely identified by its ID (`$.id`).

Given the same ID, the latest version of a summary you received **replaces** all its previous versions.

## Timeseries types

Each timeseries sample is uniquely identified by a compound key of:

* the timeseries resource type;
* the source provider;
* the [Source Type](/wearables/providers/data-attributions#source-type); and
* the sample timestamp.

Given the same compound key, the latest value of a sample you received **replaces** all the previous values.