Shutterfly

Shutterfly Customer Lifetime Value Code-Challenge

Critical Design Decision

1. For any event if the required data is missing or has null value, then that event's data would not be ingested into the in-memory Data Structure.
2. An additional Data Structure has been created to handle the events which occur in an unordered way, like:
   • A new order comes before the create event for that particular customer
   • An Updation to an order comes before creation of that order
3. The events are processed in such a way that all the ordered events will be ingested in the in-memory Data Structure, and all of the unordered events are inserted into the additional Data Structure.
4. Once all the ordered events have been processed then the additional Data Structure will be processed to inserts the unordered event in the in-memory Data Structure.
5. Since revenue / visit and visits / week are important metrics to the business so, there are two functions revenuePerVisits & visitsPerWeek which help in achieving these functionalities.

Performance characteristic

1. Keeping Performance in mind I have tried to use HashMap for the in-memory Data Structure instead of lists, wherever frequent searching is required, so that we can reduce the lookup time to O(1).
2. I have used Priority Queue to fetch the top X Customer Lifetime Values which will give us the least completxity.

Assumptions

1. Average customer lifespan for every customer is 10 years.
2. If an order has been placed then it is assumed that, there is also a site_visit entry in the input data corresponding to that order.
3. While updating customer we are just updating last_name, adr_city, adr_state and not event_time because if we update it, we will lose the customer creation date which is necessary for LTV calculation.
4. While updating orders we are just updating event_time, total_amount and not customer_id because we need to preserve customer id corresponding to a particular order.

External Libraries Used

Gson --> 'gson-2.2.3.jar' http://www.java2s.com/Code/JarDownload/gson/gson-2.2.3.jar.zip