Rakuten Advertising Software Developer interview questions

I was contacted by the recruiter who found my profile on linkedin. After initial chat, he set up a call with the hiring manager. The call went well. I was asked mostly about stuffs in my resume and also a couple of technical questions on list duplicates and their time complexity. Then I was asked to complete a programming assignment and submit the same within a week. The assignment wasn't difficult but needed some thinking to handle concurrency issues. After I submitted, I didn't hear back from them. I emailed them about 4/5 times but to no avail. Not even a rejection email. This shows how unprofessional their whole process is. Please don't waste somebody's time if you are not bothered to even reply to emails.

Applied online and received a call from hr for a phone screen. While the interview went very well, the interviewer was pretty patronizing but seemed satisfied with my interview. I then received a ridiculous assignment which I had to do which was not at all relevant to my position neither was it in my resume/skillsets (the assignment was related to front end while this was a backend infrastructure position). On telling the hiring manager this, he still insisted I do the assignment. So after spending a couple of days learning these technologies which I mostly wont use in the job, I received a rather rude rejection email as I did not complete some part which was not even mentioned in the description. Terrible experience and an utter waste of my time.