---
title: "The index property store"
slug: "the-index-property-store"
abstract: "The index property store persists metadata for search indexes."
---
# The index property store
The index property store persists some metadata for search indexes. For example, the last updated timestamp is in the index property store.
You configure the index property store in the `sitecore/contentSearch` part of the `Sitecore.ContentSearch.Lucene.DefaultIndexConfiguration.config` file. The configuration delivered with Sitecore looks like this:
```xml
$(1)
core
```
This index property store configuration uses the Properties table in the Sitecore database as the persistent store, and it uses the `core` database.
You assign the index property store to each index with this configuration:
```xml
$(id)
$(id)
```
You must set the first `param1` attribute to `$(id)` or something similar. It must be unique across all indexes.
The index property store is a key/value-based storage. The key consists of a master key and the key of the record that has to be saved.
The master key depends on the configuration. In the example above, the `Key` parameter of the `databasePropertyStore` definition node `($(1))` will pick up the first parameter from the place where `databasePropertyStore` is referenced:
``
Because this record is defined in the `` element, the value of `$(id)` will be `content`:
``
This is how the `databasePropertyStore` guarantees that keys are unique across all indexes. It also appends the `InstanceName` to the master key, and this guarantees that keys are unique across all environments.
With the configuration described above, you can save a custom property to the index property store with this code:
`index.PropertyStore.Set("docs-count", "123");`
The value `123` is saved with a key similar to this: `content_CM01_docs-count`, where `content` is the index ID, and `CM01` is the name of the Sitecore instance.
A custom index property store
If you cannot use the implementation delivered by Sitecore, you can create a custom index property store implementation by implementing the `IIndexPropertyStore` interface.
When you have implemented this interface, you need to define it in the configuration and assign it to indexes. You must define it in the `` part of the configuration, for example:
```xml
$(1)
$(dataFolder)/indexpropertystore
...
$(id)
$(id)
```