Round 1: LP questions and the below -

Given list of error code and time (503, 31536000), (503, 31536001), (400, 31536022), (500, 31536022)
Return all error codes which occur more than N times in a span of one hour

Round 2 (bar raiser): LP questions and Object Oriented design on parking lot

Round 3: LP questions and system design - pastebin

Round 4: LP questions and LRU cache

Did well in all the rounds except the coding question in the first round and got a reject.