Meta Interview Questions — Page 183

Meta·Software Engineer·Technical Phone Screen

Jun 2026

Meta software engineering interview with two algorithmic problems back to back. Both were coding-focused with complexity analysis required, which I half-expected but still felt the pressure on the second one.

Given an array of integers in [0, 255] representing bytes, determine whether the sequence encodes valid characters under a variable-length encoding scheme. Single-byte characters start with bit 0, multi-byte characters use a specific prefix pattern for the first byte and 10xxxxxx for continuation bytes, and the sequence must not end mid-character. Return true or false and explain your time and space complexity.
Given an n×n binary grid where 0 means open and 1 means blocked, find the shortest path from the top-left to the bottom-right cell using 8-directional movement. Count both the start and end cells in the path length, and return -1 if no path exists. Discuss your algorithm and its complexity.

“This one looked like a bit manipulation problem but it's really just careful state tracking.”

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Meta·Machine Learning Engineer·Technical Phone Screen

Jun 2026

Meta ML engineer screen focused entirely on attention mechanics. One question, pretty deep, they wanted you to write it out by hand and then defend your implementation choices.

Implement the forward pass of single-head scaled dot-product attention by hand, including masking and numerically stable softmax. Then walk through time complexity and at least two edge cases.

“This felt manageable until they asked about numerical stability and I had to actually justify the max subtraction trick rather than just mention it.”

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Meta·Data Scientist·Technical Phone Screen

Jun 2026

Meta Data Scientist technical screen, heavy on algorithms with a binary tree problem that had a bunch of follow-ups baked in. The interviewer pushed hard on space complexity and wanted an iterative version too, which I was not fully ready for.

Given the root of a binary tree, find its diameter (the number of edges on the longest path between any two nodes). Implement a DFS that returns both the subtree height and the best diameter found so far as a tuple, without using any global variable, external list, or array.
Why does storing traversal state in a list during DFS inflate space complexity from O(h) to O(n), and what tree shapes make this most costly?
Write an iterative postorder traversal version of the diameter solution using an explicit stack, while still keeping auxiliary space at O(h).
State and justify the time and space complexities for both the recursive and iterative versions of the diameter solution.

“I knew the diameter problem well enough but the tuple-return constraint threw me a bit.”

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Meta·Software Engineer·Technical Phone Screen

Jun 2026

Meta SWE coding question, pretty straightforward array problem but the 0-indexed k thing is easy to fumble if you're not paying attention.

Given an integer array and an integer k (0-indexed), return the k-th largest element in the array.

“The 0-indexed part is where people slip up.”

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Meta·Software Engineer·Onsite - Behavioral / Leadership

Jun 2026

Meta software engineer loop, mostly behavioral with a resume deep-dive at the end. Nothing technically brutal but the soft-skills questions had more layers than I expected.

How would you explain what an API is to someone with no technical background?
Tell me about a time you worked well as part of a team, and also a time you had to deal with a difficult coworker.
What's the biggest professional mistake you've made, what did you take away from it, and how did it change how you work?
Walk me through a project from your resume where you had the most impact.

“I went with the restaurant analogy (waiter takes your order to the kitchen, brings back food) and it landed fine.”

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Meta·Software Engineer·Technical Phone Screen

Jun 2026

Meta phone screen, looked like a follow-up to a BFS grid problem with a twist thrown in mid-session. The one-way cell constraint made it more interesting than a standard shortest-path question.

You have a grid where some cells are one-way intersections that force movement in a specific direction. Modify your BFS solution to handle these directional constraints and still return the shortest path.

“The base BFS I had was fine but the one-way cell part tripped me up for a bit.”

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Meta·Data Scientist·Technical Phone Screen

Jun 2026

Meta DS interview focused on a pretty involved SQL question tied to e-commerce promo analysis. One question but it had multiple layers, so it took a while to work through. Not a bad experience overall, just dense.

Given an orders table and a users table, write a SQL query that calculates the proportion of orders meeting all of the following: placed via mobile, order amount over 50, order date within the last 30 days, used a promo, and made by a US customer. Then join with the users table and define at least two additional business metrics of your choice, providing SQL and a one-sentence justification for each.

“The multi-condition filter part was fine, I set up a CTE to separate the denominator (all orders) from the numerator (filtered orders) and used conditional aggregation.”

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Meta·Software Engineer·Onsite - System Design / Architecture

Jun 2026

Meta Research Engineer system design round focused entirely on a real-time dwell prediction system for a TikTok-style image feed. Dense question with a lot of moving parts and I definitely didn't get to all of them cleanly.

Design an ML system for a TikTok-style image feed that predicts in real time how long a user will dwell on a post, then auto-scrolls to the next post once the predicted dwell time is exceeded.
How would you handle cold-start users in this dwell prediction system, and what privacy constraints affect your personalization strategy?
What guardrail metrics would you set up alongside engagement metrics when running A/B tests for this auto-scroll feature?

“I spent too long debating regression vs classification upfront and the interviewer had to nudge me to move on.”

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Meta·Data Scientist·Technical Phone Screen

Jun 2026

SQL-heavy technical screen for a Data Scientist role at Meta. Two questions, both centered on the calls table, and the hints they gave were basically the solution outline so it wasn't as brutal as it sounds.

Write a SQL query to return the top 10 users who initiated the most calls in the last 7 days.
Write a SQL query to find what percentage of active users in France were on a video call yesterday.

“Pretty standard stuff.”

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Meta·Software Engineer·Technical Phone Screen

Jun 2026

SQL round at Meta for a data engineer role. One question, pretty focused on modeling follow relationships correctly. Not a lot of fluff, just write the query and explain your logic.

Given an events table with columns for user_id, target_id, event_type, and event_time (where event types include 'request_follow', 'follow_success', 'follow_reject', and 'unfollow'), write a SQL query that returns the current count of active follow connections. A connection counts as active only if there's been a 'follow_success' with no subsequent 'unfollow' for that same user-target pair.

“The part that trips people up is the 'no subsequent unfollow' condition.”

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