1st interview: asked to describe a bug and how I resolved it in one of my projects. Then asked to Serialize a binary search tree, i.e. give a string representation of a BST. At the end there was time for questions.
2nd Interview:
Casual. Asked about some code that I had on GitHub. Asked about my background in CS. Anytime I mentioned something, e.g. regex or relational databases, he would ask for a simple example confirming I actually knew it.