Indexing is the process of sending an object to the Optimizely Search & Navigation service for storage and analysis, so it can be retrieved as search results. If a document of the same type and ID already exists, it is overwritten. The [.NET client API](🔗) supports the indexing of any .NET object.

Because objects are serialized upon indexing, the only restriction on the object is serializable. If for some reason, typically circular references, an object cannot be serialized, the API supports customizing how an object is serialized and indexed. This flexibility can also be used to implement functionality, such as indexing the return value of extension methods.

## Mappings in Optimizely Search & Navigation

When data is indexed into the search and navigation service, each property on your object indexed is mapped into different fields in the data storage engine. Each property on the object produces several fields in the storage or search engine to search in the fields using different models for tokenizing the data in the property. This metadata is stored within the search engine and is called _mappings_. The larger the mappings grows, the more load is put on the search engine, and can make the service produce high latency, or unavailability in the worst case.

You should limit the number of properties and fields in your objects that will be indexed into the Optimizely Search & Navigation service.

Especially avoid using large dictionaries, or dictionaries with dynamic data in them that is constantly changing, because the mappings in the search engine never gets deleted, and constantly grows. In the end, the search engine is using RAM and disk space to store those fields because data structures are created to search and aggregate them, which can get costly with large amounts of fields and degrade performances.

## Index using local or service queue

The indexing process uses a local queue on the site by default. The local queue is used when content is saved, published, moved or deleted. A reference is stored in the queue together with its operation, and another thread is pulling items from the local queue every 5 seconds for indexing. This procedure makes indexing more efficient, reducing number of requests from the site to the service.

**[New in Optimizely Search & Navigation version 13.4.2]**

In version 13.4.2, a _service queue_ was introduced which can be used instead of, or together with, the local queue. The service queue is disabled by default, but can easily be enabled. The service queue speeds up the indexing job on the site, because the indexing/bulk/delete request will be returned once the items have been put into a queue. The indexing processor will index the content in the order they come in. Search performance is prioritized over indexing time, with the possibility to delay indexing during high peaks.

To **enable** the service queue, add `"disableServiceQueue=false"` in the `episerver.find` element. Open the _web.config/app.config_ file and add the attribute as in this example.

You can disable the local queue in a similar way, using the `useLocalQueue` attribute.

## Index objects

Indexing is done via the `Index` method, exposed by the `IClient` interface. If you have an instance of a `Client` and an object to index, you can index using this code.

You can index several objects in a batch.

Once an object is indexed, an instance of the `IndexResult` class is returned. Use that class to verify that the indexing was successful and retrieve the document ID.

## Time delay

After an object is indexed, it is instantly available for retrieval via the `Client` `Get `method. However, before the object is returned in search results, the index must be refreshed. This happens automatically every second. However, if it is crucial that an object be available immediately, modify the client command that tells the service to refresh the index. Only do this if _really_ necessary (and preferably only while testing or debugging), since it can negatively affect performance.

## Identity

Unless specified, the service automatically assigns an ID to an indexed document. To explicitly specify an ID, either modify the command or annotate a property on the indexed class with the ID attribute. In both cases, the ID's value must be compatible with the `DocumentID` type.

You can also modify the `Client` class conventions to use a specific property or method as the ID for _all_ instances of a type without modifying the actual class.

## Ignore properties

To exclude individual properties in a class from being indexed, annotate them with the `JSONIgnore` attribute. You can also exclude properties without modifying their classes via `Client` class conventions.

## Customize type indexing

There are several ways to customize how type is serialized and indexed. You can exclude properties, remove HTML tags in string properties, and include return values of methods so they can be used later when searching or filtering.

## Update a single field

You can update a single field if you have the indexed item's ID.

## Limit the depth of ContentAreas to be indexed

You can modify a JSON contract to limit the maximum depth of `ContentAreas` to index. If your site architecture features a complex structure of nested `ContentAreas`, using the limit should improve the performance of indexing and searching.

## Size of index requests

When performing index requests, you should not exceed the maximum request size (by default, 50 MB).

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Note

Maximum size refers to the base64 encoded file size, which means that the maximum is effectively 37 MB.

If a batch exceeds the maximum and is rejected by the Optimizely Search & Navigation service, the Optimizely Search & Navigation client downsizes then attempts a retry. In some cases, you could improve performance by limiting batches to a size less than the maximum.

You can implement code that adjusts batch sizes. Specifically, you can control `ContentBatchSize` (for content) and `MediaBatchSize` (for event-driven indexing), as illustrated below. With the Find indexing job, only `ContentBatchSize` applies.

The method illustrated below, `IsFileSizeLimitReached`, which could be used in a convention, has two goals:

• Adjusts batch size

• Avoids attempts to index files that exceed the maximum