CareerCup

Sounds quite reasonable, but could you please share some piece of the code, it's easier to read code sometimes

Propose an estimate based on msg operation

Publish: add msg to all the friend's msg list
GetNewsFeed: process all the msg attached to the user

Each user, there's a msg list

UserInfo {
  MessageNode *msg_list;
  FriendNode *friend_list;
}

void Publish(UserInfo user, string msg) {
  // for each friend, insert msg into their msg list
  foreach friend in friend_list
    insert msg into User[friend].msg_list;
}

void GetNewsFeed(user) {
  foreach msg in msg_list
    process msg
}

Assume
user num: 1M
avg friend_num: 1k
msg/user/second: 0.001

Consider Publish
msg insertions per second: 1/user/second, 1M total insertions/second

Consider GetNewsFeed
user num: 1M
avg friend_num: 1k
msg read operation/second/user: 1
total msg read operations: 1M

2M total msg operations/second
Assume server capacity = 1k msg operations/ server
num of servers: 2k