New listing alerts for saved rental searches

Design alerts for a rental listings site. Renters save searches (city, neighborhoods, price range, bedrooms, pets allowed) and choose instant alerts or a daily email. When a new listing is published, or a listing's price drops into a saved range, matching renters should get a push notification or email within 5 minutes, and nobody should be told about the same listing twice. The site has 400,000 saved searches and about 15,000 new or changed listings a day, and landlords sometimes bulk-upload hundreds of listings at once. Describe how listings are matched to saved searches, how alerts are queued and sent, and how duplicates are prevented.