Karat interviewed me as a senior java dev (10 years+ experience) for Coinbase.
First question: To design an API for social media feeds.. no coding here just method definitions and results retuns

Second questions: Given an String[][] of string values pairs of people's logs of entering and exiting a building, produce a list of names of people who (1) entered without exit, (2) exit without enter.

Input sample: [Sarah, john, Sarah, Mike, Abdul, Sarah] [enter, exit, enter, enter, enter, exit]

Should not be particularly difficult if you make sure all cases are covered but I struggled with not being able to debug or write test cases as I went along, as the Karat IDE is very primitive. Spent most of the time battling that and stuff that any modern IDE would just do for you.

Make sure you can solve such a thing with Notepad essentially. Frustratingly bad way to test developers, essentially people who don't write tests or debug as they go along and instead wite code top to bottom like a letter will do well.