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You can define filters on incoming queries that MongoDB Realm evaluates and applies before its initial query to your MongoDB cluster. Adding a filter to a collection allows you to control the shape of queried documents using projection filters and can improve query performance by reducing the number of documents for which Realm needs to evaluate a role.

Every filter consists of an Apply When expression and a Filter Query document. When Realm receives an incoming MongoDB query, it evaluates the Apply When expression of all filters on the collection and merges the Filter Query document into the incoming query.

This guide walks through creating one or more filters for a collection.


This guide requires a linked MongoDB Atlas data source.

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