Twilio is setting up its Bangalore operations. I interviewed for the Senior Software Engineer 2 position through the Twilio talent acquisition team. I had six rounds of Zoom interviews with panels from the US and Europe offices. The whole process lasted for a week.

1. The first round was a screening round. It comprised a fairly simple problem-solving question for which I had to write code. The second question was a design problem, where the output requested was just the API design requirements. The purpose was to check the candidate's basics and their approach to the problem.

2. The second round was a pure problem-solving round where the candidate was required to code the problem in 40 minutes. Make sure to discuss the kind of solution required by the interviewer. I made the mistake of going for a complex solution and skipping the relatively simpler solution that the interviewer was looking for. So, communicate every thought process.

3. This was more of a behavioral round with a few technical scenarios. This was again with the Director. Focus on giving precise answers regarding situations, specific goals, results, etc.

4. This was a pure design round conducted on the sketchboard and Zoom. I was asked to implement a billing system end-to-end. The main thing to remember in this round is to provide reasons for your design choices and discuss the pros and cons of those choices. As these rounds are open-ended, communication is very important so that the interviewer and candidate are on the same page.

5. This was a complete behavioral round. The panel was looking for the presence of Twilio's core values in the candidate. Again, don't give generic answers. If you have ever experienced any of the circumstances asked, answer in detail about the specifics; otherwise, just convey that you haven't encountered those situations.

6. The last round was a mixture of problem-solving and design, where I was asked to code the solution. I did not repeat the mistake of going for the most optimized solution in one go but discussed all the solutions and finally implemented one that the panel requested.

Design and implement a rate limiter.

Design a billing system with third-party APIs.