Given users, books, and checkout data, find the number of users who checked out books in the geography category grouped by age.

"I interviewed for Meta IC5 Senior Data Engineer, and the process felt hard but achievable if you prepare the right way. The first big hurdle was a live 1-hour CoderPad screening with 3 SQL and 3 Python questions, and the hardest part by far was the time pressure. After that, the onsite was four rounds and felt much more analytical than other DE or backend loops I've done, especially around SQL, data modeling, and tradeoff thinking. The round that stood out most was designing an Uber-style data model and then defending scaling choices like bucketing and hash-based partitioning once the table size went past 1 TB. Overall, it felt very SQL-heavy and very focused on whether I could show real technical depth, not just solve toy problems."