Rafay Systems Developer interview questions

There were supposed to be 3 technical rounds and 1 HR/Managerial round. The first was a small Aptitude+Core CS+ 1 Coding Question. The coding question were(1 out of 3): 1. Balanced string of (,[,{ (Easy) 2. Next Greater Element. (Medium) 3. Validate if a given binary string is BST. (Easy-Medium). After this, there were supposed to be 2 technical rounds 45 mins each, 1st focusing more on DSA, and 2nd focusing on resume, but mine was a lil different. My interview lasted a little longer ( around 10 mins) where it was half resume and half DSA, where interviewer asked me to do the Next Greater Element and then a basic graph question. He was helpful and cleared wherever I got stuck. However, after this round, I was asked to appear for Managerial round directly after 3 days, and I got rejected at managerial stage😭. However, I am told they are looking to increase headcount, and if they do, then I am the first backup. I don't really know if they actually meant it or just were being polite. Let's see...🤞 The management was fine, the interview was onsite, but they provided meal and the HR was helpful. Overall, great interview experience, but maybe I lacked somewhere, and will work on myself. Plus there's one complain: I was not given a feedback.