Notify Users on User Defined Events on Data changes on server

I have a node.js webservice with 10k users.each user can monitor price changes of 1k items(realtime or every second). my problem started here: each user can listen 4 event : start/stop/higher/lower for each item. when event fired i need to send sms or email to user. which design pattern or database model i need to implement this ? how to implement it? any book or reference? thank you