db={"users":[{"id":1,"name":"user1","subscriptions":[["doha","tv","used"],["dubai","flat","sale"]]}],"posts":[{"id":1,"title":"Tv for sale","city":"doha","tags":["doha","tv","sale","used"]},{"id":2,"title":"flat for rent","city":"dubai","tags":["dubai","flat","rent"]}]}

db.users.aggregate([{"$lookup":{"from":"posts","let":{"subs":"$subscriptions"},"as":"posts","pipeline":[{"$match":{"$expr":{"$reduce":{"input":"$$subs","initialValue":false,"in":{"$or":["$$value",{"$setIsSubset":["$$this","$tags"]}]}}}}}]}}])