📌 Facebook | E5 | Bay Area | Virtual Onsite

I recently had a virtual onsite interview with Facebook for an E5 Software Engineer role in the Bay Area. The process involved four 45-minute rounds: two focused on coding, one on system design, and a behavioral round which surprisingly also included a small coding problem.

1st Coding Interview

The first coding round started with a problem similar to Intersection of Two Linked Lists, but presented in the context of a binary tree. I was asked to find the Lowest Common Ancestor (LCA) of two nodes in a binary tree, where each node only had a parent pointer. Initially, it took me a moment to connect it to the linked list intersection concept, but I eventually figured it out without any hints. I implemented a two-pointer solution in Java, achieving O(n) time complexity and O(1) space complexity. After walking through my code with a few examples, the interviewer seemed pleased. We then moved to a second coding question: Leftmost Column with at Least a One, which was identical to the problem found on LeetCode. I provided an optimal solution for this as well.

2nd Coding Round

In my second coding round, I tackled two problems. The first was Range Sum of BST, and the second was Trapping Rain Water. Both were exactly as they appear on LeetCode. I developed optimal solutions in Java for both. For the first question, the interviewer requested a few examples and base cases to test my solution. Unfortunately, we ran out of time before I could thoroughly walk through the solution for the second problem.

System Design Interview

The system design interview challenged me to design a Proximity Server. The core requirement was to, given a location's latitude and longitude, find all nearby places within a specified radius. I began by clarifying the essential features and discussing the design goals and potential scale. I then outlined a high-level design of the APIs. A significant portion of my discussion focused on the data structures and algorithms for efficiently finding nearby places; I proposed using a Quad Tree to represent geographical grids and store locations. I also delved into sharding strategies, briefly explaining Consistent Hashing, and the importance of caching for quick data retrieval. Additionally, I touched upon the application layer, mentioning stateless machines and load balancers. I later found a helpful video on this topic here.

Behavior Round

The behavioral round primarily centered on my projects at my current company. The interviewer also posed questions related to conflict resolution, how I've made an impact outside my immediate team, and my approach to problem-solving when faced with limited information. For each of these, I drew upon my past experiences to provide concrete examples. Towards the end, a simple coding problem was introduced: Valid Palindrome. I believe I performed well in this round, effectively communicating my experiences and solving the coding challenge.

Overall, I feel the interview went quite well. I've received an email from the recruiter indicating that it might take up to a week to hear back about the result. So, I'm keeping my fingers crossed!