Meta Software Engineer Interview: Rounds, Questions and Preparation

What the job involves

Software Engineers at global tech companies like Meta design, build, and maintain large-scale software systems that serve billions of users. Day to day, they write code, review peers' code, debug production issues, and collaborate with product managers and designers to ship features. Freshers typically start on well-scoped components or features with mentorship, focusing on clean code, testing, and scalability.

Role and Technical Knowledge

1. 1

   Explain the difference between an array and a linked list, and when you would use each in a large-scale system.

   Cover memory layout, access time, insertion/deletion costs, and cache performance. Mention real scenarios like frequent insertions vs random access.

2. 2

   What is a hash table and how does it handle collisions? Give an example of its use in a social media feed.

   Describe hashing, collision resolution (chaining, open addressing), and load factor. Relate to storing user sessions or deduplicating posts.

3. 3

   Explain the concept of time complexity. How would you analyze the complexity of a recursive function like computing Fibonacci numbers?

   Define Big O, discuss recursion tree, and contrast naive recursion (O(2^n)) with memoization (O(n)). Show awareness of space complexity.

4. 4

   What are the ACID properties in databases? Why are they important for a payment system?

   Define Atomicity, Consistency, Isolation, Durability, and explain how they prevent partial transactions or data corruption in financial contexts.

Practical Scenarios

1. 5

   You are asked to design a feature that shows the top 10 trending hashtags in real time. How would you approach it?

   Discuss data ingestion, counting with sliding windows, using a min-heap or count-min sketch, and caching. Mention trade-offs between accuracy and speed.

2. 6

   A bug is reported where users sometimes see an old version of their profile after updating. How would you debug this?

   Outline steps: reproduce, check caching layers, database replication lag, and client-side cache. Suggest logging and monitoring to isolate the issue.

3. 7

   You need to store and retrieve millions of user posts efficiently. What database would you choose and why?

   Compare SQL vs NoSQL, discuss sharding, indexing, and read/write patterns. Mention that choice depends on consistency needs and query flexibility.

4. 8

   How would you test a function that calculates the average rating of a product from user reviews?

   Cover unit tests for normal, edge (empty list, single review), and error cases. Mention mocking external dependencies and boundary values.

Behavioural and HR

1. 9

   Tell me about a time you worked in a team to complete a project under a tight deadline.

   Use STAR method: describe the situation, your task, actions you took (prioritization, communication), and the result. Highlight teamwork and outcome.

2. 10

   Describe a situation where you had a disagreement with a teammate. How did you resolve it?

   Focus on active listening, data-driven discussion, and compromise. Show you value the team's goal over being right.

3. 11

   Why do you want to work at a global tech company like Meta, and how do you handle feedback?

   Connect personal goals to the company's mission and scale. Give an example of receiving and acting on constructive feedback.

4. 12

   What is a project you are proud of, and what was your specific contribution?

   Choose a project that showcases technical skills and impact. Be clear about your role, challenges, and what you learned.

Problem Solving and Coding

1. 13

   Given a list of user IDs and their friends, find the number of mutual friends between two users.

   Model as sets, iterate through the smaller set, and count intersections. Discuss time complexity and potential optimizations.

2. 14

   Write a function to reverse a linked list iteratively and recursively.

   Show both approaches, handle edge cases (empty list, single node), and explain pointer manipulation clearly.

3. 15

   How would you find the first non-repeating character in a string?

   Use a hash map to count frequencies, then iterate to find the first with count 1. Mention O(n) time and O(1) space for fixed alphabet.

4. 16

   Given a binary tree, write a function to check if it is a valid binary search tree.

   Use in-order traversal or recursive min/max bounds. Discuss why checking only immediate children is insufficient.