AppNexus Technology interview questions

Interview was good but i was selected for the role , but they offer me the unpaid internship for three months just because i am pursuing btech and in my final years currently. so i reject the offer because i was thinking about the college placements

The first round was the telephonic round where he asked basic questions to check the eligibility, The second round was the on-site problem-solving round, where they asked me to create an API endpoint to filter the objects (ley say a store ) with the help of a database query and express. The third round was again a technical one to check the tech stack knowledge I mentioned on my CV.