The GraphQL API indexes on collection fields to provide sorted results when using the sort parameter. If a filter is specified, the existence of an index can have a large impact on how quickly a query executes.

Things to keep in mind with indexing:

By default, all primary fields on a collection are indexed.
Indexing of text fields is limited to the first 100 characters.
Object fields on a collection are always excluded from indexing.

Improving Filtering Performance

The GraphQL API always attempts to use an appropriate index when executing a query. The sort parameter takes precedence over the filter, though, which means sorting by one field and filtering by a different field may result in a slower query execution.

To improve query performance in scenarios like this, a multi-field index is recommended (as described here). If, for example, we want to get only documents in a specific category, sorting by date, a multi-field index should be defined, with the category as the first field, and the date as the second field.

It is important to remember that the sort field must be specified in order for an index to be used. If no sort is specified, all items in a collection will be scanned (in filename order).