Braintree Software Engineer(Internship) interview questions

-OOP Coding Challenge with implementation of a simple credit card system -Phone Interview about technical/professional background -5-round onsite interview: Technical Background/Whiteboarding, Lunch Interview, Product Design, Revamping code from Round 1, Talk with Hiring Manager

I talked with Braintree for the first time at my college's career fair. I talked to a current software engineer and was told (if anything) I would be contacted by a recruiter for a coding challenge. About a week to two weeks later, I got an email to start the coding challenge. I was given a week to complete it. The next business day(after submitting) I got a call which I was told I was moving onto the next round which was a phone interview. I talked to two other engineers currently at Braintree and we talked about previous projects I have worked on. Mostly talked about how I went about solving the project, testing, any road blocks, etc. I got a call a day or so after saying they wanted me to come onsite for an interview. The onsite interview was all day (10am - 4:30 pm) and consisted of 4 main parts. The first part was an hour and half where I talked with 2 engineers about past projects again as well as solved some "puzzle problems". The next part was lunch (1 hour) with a different set of engineers where we talked more casually about Braintree as a whole and they asked me questions about past projects but nothing too in depth. The third part was product whiteboarding with another set of engineers(hour and a half). They give you some kind of app and you need to go through and talk about how you would make it. This is more of a conversation than me talking to them. The last section was with yet another set of engineers where it is a pair programming session. They pull up your coding challenge submission and ask to make some kind of extension on it. As I did this I had to explain what I was doing during each step.