Meta E4 | Onsite | Reject

I interviewed for an E4 position at Meta, starting with a phone screen. I was given the LRU Cache problem, which I solved optimally using a doubly linked list and hashmap. The interviewer indicated that one question was sufficient due to its length. He then gave me a conceptual question very similar to Daily Temperatures, asking only for an explanation of the solution. I cleared this round and proceeded to the onsite interviews.

The onsite consisted of two coding rounds, a behavioral round, and a system design round. In the first coding round, I solved a fairly simple problem to find the moving average within a given window (e.g., [1,2,3,4,5,6,7] k = 3 output [2, 3, 4, 5, 6]), which was a straightforward solution. This was followed by the Word Ladder graph problem, which I knew and coded smoothly.

The second coding round included a simple question similar to Valid Word Abbreviation, which I coded and walked through in about 5 minutes. The second question was similar to Binary Tree Right Side View, which was also simple, and I quickly completed the code and walkthrough.

My behavioral round was one of my best. The interviewer was very kind and friendly, and we spoke about some of my complex projects and how I solved problems within them.

The system design round was where I struggled. I was asked to design a library that, given a URL, downloads files from outside. The interviewer provided a function definition func($url, ?= parameters) and directed me to focus on the client-side, seemingly judging my JavaScript abilities, specifically focusing on concepts like promises and threads. I kept answering based on what I thought would be a good design for such a library, and he asked questions about thread counts and safe numbers. Upon doing some research afterward, I found the problem was similar to a mobile system design exercise. Despite my extensive preparation in backend system design, this mobile-focused problem caught me off guard. I was ultimately rejected, and I believe my performance in this round was the primary reason for the outcome. I was fairly disappointed as I had prepared extensively for backend system design.