let users: Observable<User[]> //all the users

let receivedUsers: Observable<User[]> //only a subset of users get from http

receivedUsers: [1]  .... [2]    ..... [3,4]       ..... [5,6]

users        : [1]  .... [1,2]  ..... [1,2,3,4]   ..... [1,2,3,4,5,6]