> In theory you could write a pretty simple SQL query, and sure, Big Tech companies have giant data warehouses where you can easily do this sort of thing. But for the scope of a coding interview, you wouldn’t want to. Since this is not a distributed systems problem and the data fits in memory, why introduce the additional complexity and dependencies of a database for something that you can solve with 20 lines of simple code?
My first thought on an actual implementation was, if this is a one-off request, to import it into sqlite. No need to set up a big system, and I think it would be easier/faster than writing those 20 lines of code. Also a hell of a lot easier to iterate on minor spec tweaks like the unique pages overall vs per day clarification. And probably less likely to have off-by-one type of bugs, since the simple logic is handled by the database itself. Bonus, it does handle the case where the dataset is larger than memory!