The realestate.com.au website and mobile applications are used by 12.7 million people on average each month in their search for property. Users can save their search filters so that they may easily repeat searches later. Once a user has saved a search, they have the option to receive daily notifications of new listings that match their search criteria. Supporting this involves matching the thousands of new listings created every day against millions of saved searches. In this article I explain how we use Elasticsearch’s “percolation” feature to help us do this.