10.3

Suppose you wish to store utility bills for a large number of users, where each bill is identified by a customer ID and a date. How would you store the bills in a key-value store that supports range queries, if queries request the bills of a specified customer for a specified date range.

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Create a key by concatenating the customer ID and date (with date represented in the form year/month/date, e.g., 2018/02/28) and store the records indexed on this key. Now the required records can be retrieved by a range query.