Facebook Interviews

I recently navigated the onsite interview process at Facebook, and I've detailed the specific LeetCode problems I encountered during my rounds below. Having also interviewed with Google, Amazon, and Apple, I've developed a perspective on the relative difficulty of securing a position at each. In my experience, Facebook felt somewhat more accessible than Google, particularly if one has thoroughly prepared using the Facebook-tagged questions on LeetCode; I personally didn't encounter any questions that weren't already on LeetCode. On a difficulty scale, I'd rate Google around a 9, Facebook a 7 (or even a 5 if you've mastered their tagged questions), Apple a 5, and Amazon a 2 or 3, as it primarily focused on fundamental concepts. Although this post recounts my Facebook experience, I ultimately accepted an offer from Google, and things have been going great there. To anyone currently interviewing, keep up the excellent work – you'll achieve your goals!

Last week, I had my virtual onsite interview with facebook for the Sr Software Engineer (E5) position. The overall experience was great.

Phone Screen

This was a 45-minute round where the interviewer asked two coding questions. I focused on understanding the problem, clarifying any ambiguities, and then verbally explaining my solution along with its time and space complexity. Once the interviewer was satisfied, I quickly implemented the solution and performed a dry run with test cases, including corner cases, finally explaining the complexity of my written code.

Virtual Onsite

The virtual onsite consisted of four 45-minute rounds: two Coding Rounds (Ninja), one System Design Round (Pirate), and one Behavioral Round (Jedi).

Coding Round 1:

Similar to the phone screen, I was given two coding problems to solve, applying my structured approach of understanding, verbalizing, implementing, and verifying.

System Design Round:

I was asked to design the privacy settings at facebook. I spent approximately 40 minutes discussing the design, and used the remaining 5 minutes to ask questions about facebook's culture.

Coding Round 2:

This round also involved two coding questions, where I applied my standard approach for solving them.

Behavioral Round:

The interviewer started by asking me about myself, my current project, and significant accomplishments. I was also asked if I had ever managed conflicting priorities and if I had received constructive feedback from a colleague. For each behavioral question, I provided a supporting anecdote from my past experiences, ensuring my answers aligned with facebook's mission and core values. Interestingly, this round also included one coding question.

Two days after my virtual onsite, I received a call from the recruiter informing me that the feedback from my interviewers was good, and they are still waiting for the hiring committee to make the final decision.

Technical Phone Screen

My interview process began with a technical phone screen. I was given two coding questions, with no Android-specific problems. I successfully resolved both problems within 40 minutes, which allowed me to proceed to the virtual onsite interview.

Virtual Onsite Interview

The virtual onsite consisted of four rounds: two coding interviews, one system design interview, and one behavioral interview.

1st Coding Round

In this round, I encountered two coding problems. I managed to resolve both questions in under 40 minutes. For the first problem, I achieved an O(n^2) solution, and for the second, an O(nlogn) solution.

2nd Coding Round

The second coding round also presented two coding questions. I resolved both of these within 40 minutes, delivering an O(n) solution for the first problem and an O(n^2) solution for the second.

Design Round

The design interview focused on designing the Instagram home screen. After clarifying the requirements, I discussed authentication with Facebook, how to handle a large volume of posts, the constraint of each post having only one image, liking/disliking functionality, displaying user profile photos, and critically, how the app would support an offline mode. My discussion covered RecyclerView optimizations, image caching strategies (including the underlying mechanics of libraries like Glide/Picasso), WorkManager, batching requests, and pagination. I was initially quite nervous about this round, but I felt I performed really well in the end.

Behavioral Round

This round was primarily a conversational interview. I was asked to share examples from my past experiences related to specific situations, such as receiving ambiguous requirements or working with colleagues I disliked. I believe I handled the initial part of this round effectively. Towards the end, I was given a coding question which I resolved pretty quickly with an O(n) solution, although I think I might have missed some edge cases, like empty spaces at the beginning of the input. However, the interviewer seemed content with my solution.

Hey Everyone,

I interviewed with Facebook for an E4 role in London. I am currently waiting to hear back from them regarding the outcome of my interviews.

Phone Screen:

This round involved two coding questions. I felt confident in my ability to solve both on time.

1. Binary Tree to Doubly linked List.
2. Evaluating expression (Only with +/* operators).

Onsite Coding 1:

I successfully solved both problems presented in this round within the given time frame.

1. Multiplying 2 strings.
2. Course Schedule problem on LeetCode.

Onsite Coding 2:

Only one question was asked in this round. I was able to solve it on time, even though I required one hint from the interviewer. Overall, the interviewer seemed convinced by my solution.

1. LFU Cache Implementation.

Behavioral:

This round consisted of standard behavioral questions and some inquiries about my past work experience. I managed to tackle all the questions well, with only one or two proving to be a bit tricky.

System Design:

The challenge here was to design a system similar to Google Drive. I was able to approach the problem, but the interviewer continuously introduced new scenarios. I could answer some of these, but got stuck on others. I feel this round went below average to average.

I was referred to a recruiter by a friend who had previously interviewed at facebook. The entire interview process spanned about a month and a half, starting in March and concluding in mid-April. Each round was 45 minutes long, with coding rounds featuring two questions each.

Screening Round:

I faced two coding questions. One was related to palindromes (though the exact problem isn't shared), and the other involved finding a path in a given binary tree. For the binary tree problem, I also had follow-up questions to solve it without using a global variable and to adapt the solution for any n-ary tree. I managed to complete both questions within 35 minutes, and the feedback was very positive, leading to an E6 position consideration.

Coding Round 1:

This round also had two coding problems. The first was about merging two sorted arrays. The second involved merging contacts with domain names into the minimum number of groups; the interviewer suggested treating contacts as graph nodes, generating edges for common domains, and then using DFS for connected components. The feedback for this round was good.

Coding Round 2:

Again, two coding questions. One asked me to find an element in an array and return a random index if multiple occurrences existed. The second problem involved using two given APIs, move() and isTarget(), to determine if a target was present in a grid that contained a source and target at some positions. I solved both of these with some hints from the interviewer, and the feedback was good.

Product Design Round 1:

As I was interviewing for an E6 position, there were two technical product design rounds. The first involved designing an API for a newsfeed, similar to Instagram or Facebook, while considering multiple client types. The feedback was that I needed to discuss more about the scalability of the system.

Product Design Round 2:

The second product design round focused on designing a system to handle live comments for videos. The feedback indicated that I needed to delve more into the low-level details of the system.

Behavioral Round:

This round consisted of standard behavioral questions based on my past experience, covering situations like handling teams, conflict management, and my learnings over the last 2-3 years. The feedback was positive.

Ultimately, considering the feedback from the product design rounds, I received a rejection. The recruiter explained that product design is a very critical component for E5 and E6 positions, and despite very good feedback in other rounds, they had to reject me on that basis. I hope my experience can be helpful to others.

I had an interview for an E5 Lead Engineer position at Facebook in London. My experience level was 12 years.

Talk with the recruiter (30 mins):

This discussion was crucial for setting my expectations and understanding the interview process. The recruiter provided valuable insights and resources for preparation. I treated this as an interview itself, asking all my questions about the preparation process.

Technical Phone Screen (45 mins):

I was asked two coding questions in this round. Both were relatively easy, and the key was to articulate my thought process clearly. I made sure to test my code immediately after writing it, which impressed the interviewer.

Virtual Onsite (4 rounds):

Behavioral (45 mins):

This round focused on my past experiences in teams and how I handled technical challenges. The questions were open-ended, and each answer led to follow-up questions. I wasn't asked any coding questions in this round. My recruiter had mentioned that a strong positive signal in this round is critical, as a negative signal here can lead to a 'no-hire' decision even with strong technical performance.

System/Product Design (45 mins):

I was tasked with designing a file-sharing system similar to Dropbox. During requirement gathering, I pointed out a potential security issue with auto-sync, which seemed to impress the interviewer. My proposal for staggered scale-up based on usage trends also received positive feedback. I drove the discussion, answering clarification questions and providing high-level differences between SQL and NoSQL without getting bogged down in details.

Coding 1 (45 mins):

This round was similar to the phone screen but with a higher bar. I tackled two coding problems. The first involved a LeetCode problem, where I used Breadth-First Traversal and discussed follow-up questions on parallelization and memory constraints. The second was another LeetCode problem, which I solved very quickly.

Coding 2 (45 mins):

I faced two more coding questions here. For the first, which involved checking interval coverage, I initially missed a boundary case but caught and fixed it during testing without prompting, which was viewed positively. For the second, finding connected sub-graphs in an undirected graph, I used Depth-First Traversal. I ran out of time to complete the code, but because I had modularized my solution, I could clearly outline the remaining implementation details for the interviewer.

The next day, I received positive feedback from my recruiter for all four rounds and was informed that I would proceed to the review board. The offer came through the day after that.

I had my final round of interviews for a remote E5 position with Facebook in March 2021. The interviews were conducted via video calls, utilizing CoderPad for coding and Excalidraw for design discussions.

My first coding round included two problems: Leftmost Column with a One and Kth Smallest Element in a Sorted Matrix.

The system design round presented the challenge to "Design a Load Balancer".

For the behavioral interview, I was asked several questions: "Can you tell me about a time you had to overcome obstacles in a project?", "Tell me about a time you had a conflict or disagreement with a colleague.", "Did you ever try to change something outside of your responsibility?", and "How do you handle vague requirements in a project?". There was also a coding question at the end of this round, which was to convert an array of numbers as characters to an actual integer; for example, converting ['1', '2', '3'] to 123.

In my second coding round, I tackled Merge 2 Sorted Arrays and Insert into a Sorted Circular Linked List.

The product design round focused on "Design a client library for a mobile phone that downloads media files (image, video, music/sound)".

About a week after the interviews, I received a rejection email that did not include any specific feedback. I felt pretty good about the coding rounds, as I was able to code solutions for all of them, and practicing problems on LeetCode definitely helped. Facebook also has its own interview prep coding problems, but I found them generally much easier than the ones on LeetCode.

I'm pretty sure the system and product design rounds were my downfall. I had been preparing for designing distributed systems for those rounds, so it threw me off when the system design focused only on one particular component of a system, and the product design was about something I don't have much experience with. Those two rounds were nothing like the system design prep videos I'd seen online. I felt very unprepared for them even after about two months of preparation. Live and learn, I suppose.

I had my Facebook E5 phone screen interview, which lasted for 45 minutes. We started with a brief 3-5 minute introduction. The interviewer then clarified that the majority of the time would be dedicated to problem-solving, reserving the last 5 minutes for my questions.

The first question I encountered was Add Binary. Having practiced this problem before, I immediately explained the optimal approach, achieving a time complexity of O(max(l1, l2)). The interviewer was satisfied with my algorithm, and I quickly proceeded to code the solution in Java. After coding, I walked through my solution with a few examples. This entire segment, including discussion and coding, was completed within 10-15 minutes.

/**
 * Time Complexity: O(max(l1, l2))
 * Space Complexity: O(max(l1, l2))
 * l1 = Length of string A, l2 = Length of string B.
 */
public String addBinary(String a, String b) {
    if (a == null && b == null) {
        return "0";
    }
StringBuilder result = new StringBuilder();

int i = a.length() - 1;
int j = b.length() - 1;
int carry = 0;

while (i >= 0 || j >= 0) {
    int sum = carry;
    if (i >= 0) {
        sum += a.charAt(i) - '0';
        i--;
    }
    if (j >= 0) {
        sum += b.charAt(j) - '0';
        j--;
    }
    result.append(sum % 2);
    carry = sum / 2;
}

if (carry == 1) {
    result.append('1');
}

return result.reverse().toString();

}

Following that, the second question was Merge Intervals. Again, I was familiar with this problem and presented the optimal O(NlogN) approach. Once the interviewer approved the algorithm, I implemented the solution in Java and demonstrated its functionality with test cases. This question took approximately 20-25 minutes to complete.

/**
 * Time Complexity O(N log N)
 * Space Complexity: O(N) (Including the List<int[]> result)
 * N = Length of input array.
 */
public int[][] merge(int[][] intervals) {
    if (intervals == null || intervals.length <= 1) {
        return intervals;
    }
Arrays.sort(intervals, (a, b) -&gt; (a[0] - b[0]));

List&lt;int[]&gt; result = new ArrayList&lt;&gt;();
int start = intervals[0][0];
int end = intervals[0][1];

for (int i = 1; i &lt; intervals.length; i++) {
    if (intervals[i][0] &lt;= end) {
        end = Math.max(end, intervals[i][1]);
    } else {
        result.add(new int[] { start, end });
        start = intervals[i][0];
        end = intervals[i][1];
    }
}

result.add(new int[] { start, end });
return result.toArray(new int[result.size()][2]);

}

With a few minutes remaining, I took the opportunity to ask the interviewer two questions about their current work at Facebook. I was thrilled to later receive a call from the recruiter informing me of positive feedback from the hiring committee and that an offer would be extended.

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!

I was referred by a friend at Facebook, which initiated my interview process for an E5 level position in the Bay Area.

Recruiter Phone Screen

The recruiter asked me about the details of my current job, my reasons for leaving, the status of any other ongoing interview processes or offers, and general questions like my visa status. We also discussed the target level for my interviews.

Technical Phone Screen

This 45-minute round focused purely on coding. After brief introductions, we dove straight into two questions. I spent about 15 minutes on the first question and 25 minutes on the second.

The questions were:

1. Lowest Common Ancestor of a Binary Tree
2. Integer to English Words

Virtual Onsite

All rounds during the virtual onsite were 45 minutes long.

Coding Round 1

I was given two coding problems in this round:

1. Product of Array Except Self
2. Clone Graph

Coding Round 2

This round also had two coding questions:

1. Subarray Sum Equals K
2. Minimum Remove to Make Valid Parentheses

System Design Round

I was tasked with designing the Facebook Status Search system. I utilized an iPad to explain my thought process and draw the architectural diagrams. A related discussion can be found here.

Behavior Round

This round covered various behavioral questions including discussions about my recent projects, reasons for leaving my current company, conflict resolution strategies, and experiences with difficult colleagues. Additionally, there was one coding question that was similar to First Bad Version.

My years of experience are 11. My compensation before the interview was $310K, and after receiving the offer, it increased to $381K plus a $50K sign-on bonus.

I wish everyone the best of luck with their upcoming interviews!

I recently completed my onsite interview for an iOS Engineer position at Facebook in London. I have 5 years of experience (YOE).

In the first coding round, I tackled two standard questions, though not from LeetCode. I performed well, successfully running tests for the first question, and even though I couldn't run tests for the second due to time constraints, the interviewer seemed fine with it.

The second coding round presented one medium and one hard question, both of which I was able to solve in O(n) time complexity. This round also went smoothly.

The behavioral round involved standard questions about challenging work and my motivation for joining Facebook. I effectively answered these by sharing past examples from my career.

The fourth round, iOS System Design, was particularly engaging. My task was to design a messenger app. I felt this round went great, as I was able to discuss multiple architectural approaches for each component, along with their respective tradeoffs and scalability considerations.

My pre-screening took place in March, but the onsite interview was scheduled for October due to a hiring freeze for E4 positions. Overall, I feel my rounds went well, and I'm optimistic about potentially receiving an E5 offer. I'm now waiting for an update regarding the hiring freeze and my candidacy.

I've gathered a wide array of questions encountered by candidates interviewing at Facebook, organized by interview rounds. The compilation includes numerous Data Structures & Algorithms problems, often linked directly to LeetCode, as well as custom problem statements. System Design questions cover a range of topics from debugging server issues to designing scalable services like Google Search, Instagram, or file storage systems. Behavioral questions delve into common scenarios, personal experiences, and career aspirations. This collection aims to provide a broad overview of the types of challenges faced in Facebook interviews.