The system design questions all centered around the architecture of TTD itself; so think about scale right from the get-go if you can, rather than trying to describe something simple and iterate. The pair-programming I was quite well prepared for, since the recruiter sent a lot of info in advance. It wasn't anything tricksy, more of an exercise in refactoring. The algos-focused 1hr programming interviews were fairly standard. If you've prepared using ye olde leetcode grinding then you shouldn't have a problem. It wasn't anything really intense like dynamic programming, but it wasn't just super-basic stuff like "reverse a linked list", so I was glad I had prepared and practiced and didn't go in cold.
