Phone Screen: https://leetcode.com/problems/employee-free-time/

Onsite:
First coding round: https://leetcode.com/problems/valid-sudoku, and https://leetcode.com/problems/sudoku-solver/
Second coding round: https://leetcode.com/problems/analyze-user-website-visit-pattern/
Follow up: If you cannot store that data on a single machine, and you have very large data - how can you generate that on a distributed setup.