I was contacted by MongoDB, as they had my resume from last year. The interview process included a 45-minute technical phone interview, followed by another 45-minute phone interview. Finally, I completed three onsite interviews.

I felt the onsite interview questions were not that difficult, but I tunnel-visioned too hard on one approach and missed an easier solution.

Given a string of parentheses, brackets, and curly braces, write a function that returns whether the string is well-balanced. This means every left delimiter is closed by the correct right delimiter.

I was asked this question by multiple interviewers; it seems like their go-to question.