I applied online without any referral. After a few weeks, I got an email from the recruiter to talk about my background. Then I had one technical interview online for a coding interview in C++ related to my background. Fortunately, I passed it, and then I was invited to on-site interview. The onsite interview consists of 4 slots where I was interviewed about my research background, coding interview (leetcode), etc. Overall, my experience was positive. Everyone is kind and the office was great.