Event Driven Systems: Building A Facebook Like Counter & Notification System

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Most of the applications have some sort of badging functionality which is used to display certain counts to the users for CTA (Call To Action) Once the user clicks or acknowledges the counter, the value associated with the counter will need to be reset. Given a system with large number of users and a large data set, it's not always possible to compute the counter values in real time. Counts in the database world are aggregation operations and would need to perform a whole table scan. An alternative approach to doing count operation is to keep track of the counts in separate fields/columns.