db={"collection":[{"_id":1,"entity_id":1,"user_id":1,"created_at":"2021-05-01"}],"people":[{"_id":1,"organization_type":"school","organization":"UCLA"}]}

db.collection.aggregate([{"$match":{"created_at":{"$gte":"2021-02-01","$lt":"2022-02-01"}}},{"$lookup":{"from":"people","localField":"user_id","foreignField":"_id","as":"fromPeople"}},{"$unwind":"$fromPeople"},{"$match":{"fromPeople.organization_type":"school"}},{"$project":{"fromPeople.organization_type":1,"fromPeople.organization":1,"user_id":1}}])