Fairly trivial until the inevitable "big-O notation" question, which all these HFTs love to ask, even if it doesn't have any obvious relevance to the position being applied for.

To be fair, I found it quite a pretentious move, so I'm somewhat thankful they haven't progressed with my application, even after scoring 97% on the first coding exercise and completing that in half the allocated time.

I guess they are looking for Captain America – the best of the best of the best, sir – with honours, and an appropriate ego to boot, so you're a snug fit with the rest of the business. Having 20 years of experience also appears to be insufficient for them.

Write a Python class that implements an O(1) map across all operations, specifically item deletion and random key selection.