acceldata Software Developer (Backend) interview questions

Got a call from the HR for interview process . there were four rounds 1st round: Machine coding round : I was suppose to create an application in java where i have to implement a key-value service which should persists its state across start . Had to keep concurrency in mind . this round lasted for two hours . 2nd round question 1 : sorted array of infinite 0 and 1 , find the index of first 1 questions 2: given an array of integers find the highest number by concatenation of whole array 3rd round : system design round : implement a database , API and services for a social media platform. 4th round: general discussion with Co-founder.