I applied through college or university. The process took 3 days. I interviewed at Optiver (Mumbai) in Dec 2020
Interview
Applied via campus recruitment followed by following process and three different days :
Step 1 : Fast Math
Step 2 : Fast Math
Step 3 : Face-to-Face Interview
The questions were based on nodes and tree, few from ML
Online assessment including Hackerrank. After 2 months I received an invitation for a HR round (the classic stuff), then a technical round, take home assignment then final round split into technical then HR.
Online assessment with 30 timed multiple-choice questions. You have a minute and half for each question, Once the timer runs out you can't go back to that question. A big portion of the problems involve random walk. Some questions require an exact solution, and some are estimates.
A long and exhausting OT of a few sections. Then some interviews on standard green book questions. In between one HR interview. Final round on a take-home ML project. Overall nice experience and HR provides feedback throughout all interviews.