First a phone screening with the recruiter, then a 30 min call with the hiring manager to go over my experience, then a 3 hour panel with 30 minute interviews with senior engineers about the projects I've worked on

It was a campus placement at IIT Madras. 1st round as written test with conceptual (derivation type) problems ranging from various domains of mechanical engineering. 2nd round was technical interview where they asked questions from various aspects of mechanical engineering and my masters project the interview went on for about an hour. 3rd round was the HR round where they asked situational questions it was about 30-45 mins long