TikTok Interview Questions — Page 28

TikTok·Software Engineer·Technical Phone Screen

Jul 2026

TikTok software engineer interview that was pretty much a classic LRU cache problem. Nothing too surprising but there were a lot of follow-up angles they pushed on, so it wasn't just 'code it and move on'.

Design and implement an in-memory LRU cache with O(1) get and put operations. Walk through your data structure choices, how you maintain access order, and how updates to existing keys are handled.

“I went with the standard hashmap plus doubly linked list combo, which they seemed fine with.”

View Post

TikTok·Data Scientist·Technical Phone Screen

Jul 2026

TikTok data scientist interview focused heavily on e-commerce advertising analytics, covering everything from metric design to A/B testing to diagnosing revenue drops. Pretty case-heavy, less coding than I expected.

Walk me through one of your resume projects: what success metrics did you define, how did you measure them, and what did your A/B experiment design look like?
The business wants to grow merchant advertising revenue or merchant GMV. How would you approach diagnosing the current state and recommending actions?
Ad ROI has been declining recently. How would you investigate why, and what fixes would you propose?

“I picked a project I thought was solid but fumbled the experiment design part a bit.”

View Post

TikTok·Machine Learning Engineer·Onsite - Coding / Algorithms

Jul 2026

TikTok ML engineer coding round, four algorithmic problems back to back. The problems ranged from classic stack design to a tree path question that had a subtle twist I didn't fully appreciate until after.

Design a MinStack that supports push, pop, top, and getMin, where all operations must run in O(1) time.
Design a MaxStack that supports push, pop, top, peekMax, and popMax. For popMax, if there are multiple maximum elements, remove the one closest to the top. Discuss time complexity tradeoffs.
Given a continuous stream of integers, design a data structure that supports inserting numbers and querying the current median at any point.
Given a binary tree with positive integer node values and a target integer, determine whether there is a path starting at any node and moving only upward toward the root where the node values sum to the target. Return true or false.

“Pretty standard warmup.”

View Post

TikTok·Data Scientist·Hiring Manager Screen

Jul 2026

TikTok data scientist interview focused entirely on e-commerce risk control, which makes sense given the role but still felt pretty niche if you haven't lived in that space. Four questions, all with some teeth to them, ranging from the soft intro pitch to a genuinely tricky prioritization scenario.

Give a 30 to 60 second overview of your background in e-commerce risk control, then explain why you want to join this specific risk team and why now.
What are your top three goals for your first 30, 90, and 180 days in this role, and which specific metrics would you use to measure whether you're succeeding?
Tell me about a time you pushed back on a risk policy or threshold. What data did you bring to the conversation, what trade-offs did you put numbers on, and what happened?
If you were handed competing projects simultaneously, how would you prioritize them given a small analyst team and only about 10% of engineering bandwidth available?

“The intro part is fine, everyone has a spiel.”

View Post

TikTok·Software Engineer·Technical Phone Screen

Jul 2026

TikTok software engineer coding round, one algorithmic problem the whole session. Pretty standard sliding window territory but the details trip you up if you're not careful.

Given a text string and a pattern string, find all starting indices in the text where a substring of the same length as the pattern is an anagram of the pattern.

“Classic sliding window with frequency counts.”

View Post

TikTok·Machine Learning Engineer·Technical Phone Screen

Jul 2026

TikTok ML Engineer interview that leaned harder into algorithms than I expected. The whole session basically lived inside one problem but they kept pulling threads on it until I was pretty much out of answers.

Given an integer array, find the length of the longest strictly increasing subsequence and output one valid subsequence. They wanted an O(n log n) solution using binary search, and asked you to walk through the patience sorting idea and explain how reconstruction works.
How would you adapt the solution to handle non-decreasing subsequences instead of strictly increasing ones, and what changes are needed when duplicates are present?
How would you count the total number of distinct longest increasing subsequences in the array?
Walk through the time and space complexity of your O(n log n) LIS approach.

“I knew LIS and had done the O(n^2) version before, but the O(n log n) path with patience sorting was something I'd only half-remembered.”

View Post

TikTok·Data Scientist·Recruiter / HR Screen

Jul 2026

Screener for a Data Scientist role at TikTok that opened with a surprisingly basic finance question, felt more like a vibe check than a technical round.

What does 'credit' mean in a financial context, and why does it matter to both consumers and banks?

“Wasn't expecting this at all for a data science screen.”

View Post

TikTok·Data Scientist·Technical Phone Screen

Jul 2026

TikTok data scientist interview that went deep into experimentation statistics. One big multi-part question covering basically every corner of A/B testing you can imagine. Left feeling like I'd either nailed it or completely embarrassed myself, still not sure which.

You ran an A/B test on a video length change and got a non-significant result on your primary metric. Baseline completion rate is 22% and the product team wants at least a 5% relative lift to matter. Walk through how you'd calculate the required per-arm sample size for 80% power at a two-sided alpha of 0.05, and explain your assumptions.
How would you apply variance reduction techniques like CUPED using pre-period completion data, and if your covariate explains 25% of the outcome variance, what's the practical effect on your test's power?
Given the non-significant result, should you keep collecting data, stop the experiment, or switch to a Bayesian approach with a utility-based stopping threshold? Defend your choice.
If you're tracking multiple related outcomes alongside your primary metric, how do you handle the multiplicity problem and what corrections would you apply?
How would you design a sequential testing approach, like an O'Brien-Fleming spending function, that allows you to peek at results early without inflating your Type I error rate?

“This part I actually felt okay about.”

View Post

TikTok·Software Engineer·Onsite - Behavioral / Leadership

Jul 2026

Behavioral round for a software engineer role at TikTok. Two questions, both pretty standard career and teamwork stuff, nothing too surprising but they did push for real examples.

Where do you see your career going in the next one to three years, and what draws you to this particular role and team right now?
Walk me through how you work with others on a team, especially when there's disagreement or you need to align on a technical direction. Give a specific example.

“I had an answer prepared but it felt a bit generic once I said it out loud.”

View Post