Started off with some questions about my projects. Went a bit deep with their technical aspects.
Then he asked me what are the challenges someone could face while implementing their own HashMap. After that were some questions about OS. I think I made a minor blunder here.
Then there were two coding questions:

https://leetcode.com/problems/kth-smallest-element-in-a-bst
https://leetcode.com/problems/merge-intervals

Gave the optimal solution pretty fast and the interviewer seemed satisfied. Then there were another couple of questions about OS. Did well enough in those.
Finally he asked me if I had any questions for him. Asked about his team and what sort of things they worked on. Overall I would say I feel good about my chances of getting into the next round but not sure.