Carlos got an offer as an Engineering manager at Meta

The scale of the company and dealing with a new set of problems.

Amazon.

I spent 6-8 hours a day over 3-4 weeks. Coding prep: I did LeetCode easy until I had like 20-25 done, then I did mediums. I mostly focused on the list for Meta even though I was interviewing at other places as well. For System Design, I paid for a month of educative.io, read a couple of System Design interview books and watched a bunch of mock interview videos on YouTube (by IGotAnOffer and others). Once I was sort of ready I scheduled interviews, including my mock interview on this site. The first interviews were with companies where I was mildly interested but not really my end goal.

Watching and reading about so many different problems and understanding enough about core concepts but still dealing with things that I had never really experienced before. For example, I've never worked with WebSockets and chat apps, so answering questions on that was hard.

In my system design interview I was asked: "Design a contact tracing system and data store for COVID based on proximity signals from employee badges".

Practice, practice, practice! Interviewers don't need you to recite stuff from memory, instead make sure you know the building blocks and how to use them in different scenarios. Also, Math wasn't a big focus of any of my answers or what interviewers were particularly interested in.