In June, an HR person reached out about an MTS role, and we talked through some behavioral questions and my project experience.
Phone screen: AI coding — basically they give you some code and have you spot design pattern issues (like something not being extensible), or point out a bad data type. On CodeSignal, the AI is really strong and basically does the work for you. You just need to talk through with the interviewer roughly what needs improving. Not hard. The interviewer was friendly. Not long after this they scheduled the onsite. (HR had actually said this round would be leetcode-style DSA, but when it came to the actual interview it turned out to be AI coding.)
Onsite: First round was system design — design a customer payment dispute system. Pretty standard.
Second round was coding, and this is where I got rejected. It wasn't hard on its own — just determining whether a math expression is valid or not. Lots of corner cases. But I didn't get it bug-free, and HR said the coding didn't meet the MTS bar.
Given a string s. We need to identify if its a valid number or not.
A valid number can be either: An integer number followed by an optional exponent, or a decimal number followed by an optional exponent.
The components are defined as follows:
Integer number: An optional sign (+ or -) followed by one or more digits.
Decimal number: An optional sign (+ or -) followed by one of these formats:
- Digits followed by a dot . (e.g., "3.")
- Digits followed by a dot . followed by more digits (e.g., "3.14")
- A dot . followed by digits (e.g., ".5")
Exponent: The letter e or E followed by an integer number (which can have its own sign).
Digits: One or more numeric characters (0-9).
Examples of valid numbers:
"2" - simple integer
"-0.1" - negative decimal
"4." - decimal with trailing dot
"-.9" - decimal starting with dot
"2e10" - integer with exponent
"3e+7" - exponent with explicit positive sign
"53.5e93" - decimal with exponent
Examples of invalid numbers:
"abc" - contains letters
"1e" - exponent without integer
"e3" - starts with exponent
"99e2.5" - exponent must be integer
"--6" - double sign
"95a54e53" - contains invalid character
The task is to return true if the string represents a valid number according to these rules, and false otherwise.
Third round was BQ, with the interviewer. Standard BQ questions.
Fourth round was AI coding again, similar to the phone screen.
After the interviews, HR called and said the position was filled, and also that the coding didn't meet the bar.
Overall it wasn't hard. My coding wasn't bug-free, nothing to say about that. I'm just genuinely not good at that kind of problem.
No matter how I applied or how many referrals I tried at this company, nothing worked — in the end it was HR (a third-party firm) who reached out. Feels like it's really hard to get your resume through internally.
Wishing everyone good luck with their job search.
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