Database
[{"user":ObjectId("5a934e000102030405000000"),"followedBy":[ObjectId("5a934e000102030405000001"),ObjectId("5a934e000102030405000002"),ObjectId("5a934e000102030405000003")]}]
Query
db.collection.find({"user":ObjectId("5a934e000102030405000000"),"followedBy":ObjectId("5a934e000102030405000001")})