Database
[{"IsHomePage":true},{"IsHomePage":false,"IsTagged":true},{"IsHomePage":false,"IsTagged":false}]
Query
db.collection.aggregate([{"$facet":{"home":[{"$match":{"$expr":{"$eq":["$IsHomePage",true]}}}],"notHome":[{"$match":{"$expr":{"$and":[{"$ne":["$IsHomePage",true]},{"$eq":["$IsTagged",true]}]}}},{"$sample":{"size":50}}]}},{"$project":{"union":{"$concatArrays":["$home","$notHome"]}}},{"$unwind":{"path":"$union"}},{"$replaceRoot":{"newRoot":"$union"}}])