StackAdapt Interview Questions & Experiences

StackAdapt·Data Scientist·Technical Phone Screen

Jul 2026

Technical phone screen for a Data Scientist role at StackAdapt that went pretty deep into probability theory. The whole session was basically one branching process problem with follow-ups, which I wasn't expecting at all.

You start with 1 cell at time 0. Each minute, every cell independently dies, stays as 1, splits into 2, or splits into 3, each with probability 1/4. What is the probability the population is extinct after exactly 2 minutes?
Using the same setup, what is the probability the population eventually goes extinct at some finite time?

“I had to think through this carefully.”

View Post

StackAdapt·Software Engineer·Take-home Assignment

Jul 2026

This was a take-home case study round for a senior BI role at Stackadapt, centered on an ad spend dataset. The work expected was pretty substantial: not just crunching numbers but framing the story around them, flagging data issues, and making actual business calls.

Given an ad spend dataset, produce an analysis that includes an executive summary, data quality checks, trend and growth analysis, top and bottom market breakdowns, stated assumptions, and business recommendations.
Beyond identifying which markets have high or low ad spend, what does that data actually mean, and what are the limitations of using spend alone as a signal?

“The scope of this surprised me a bit.”

View Post

StackAdapt·Software Engineer·Technical Phone Screen

Jun 2026

Probability questions at StackAdapt for a software engineering role. Nothing crazy on the coding side but they threw in some stats/probability stuff that I wasn't fully prepared for.

Two fair coin tosses are independent. What is the probability the second toss is Heads given the first was Tails?
Given at least one of two fair coin tosses is Heads, what is the probability that both tosses are Heads? Walk through your reasoning explicitly.

“This one's straightforward if you actually remember what independence means.”

View Post

StackAdapt·Software Engineer·Technical Phone Screen

Jun 2026

Stackadapt software engineer interview had a coding portion where they gave you two domain classes from earlier in the session and asked you to write validators for both. The design angle made it more interesting than a typical leetcode grind.

Given two domain classes defined earlier in the interview, write a validation function for each that collects all field-level errors without short-circuiting, then explain how you'd structure the validation logic so both classes can share code.

“The 'collect all errors, don't stop at the first one' part is what tripped me up initially.”

View Post

StackAdapt·Software Engineer·Executive / Final Round

Jun 2026

Final round at Stackadapt for a Senior BI Engineer role. Heavy on behavioral stories but with a real technical edge, lots of ground covered around ads domain knowledge, data quality, and how you communicate messy data problems to non-technical stakeholders.

Tell me about a time you dealt with inconsistent metric definitions across teams. How did you resolve it?
Walk me through how you identified a significant data quality issue and what you did about it.
How do you handle a situation where business requirements are vague or keep shifting?
How would you design a data mart intended for business reporting? What decisions would you make and why?
Describe how you explain a complex data problem to a business stakeholder who doesn't have a technical background.
What's your understanding of how the programmatic advertising industry works, and how does that inform the way you approach data problems in this space?

“This one felt like a trap at first because every company has this problem and it's easy to give a generic answer.”

View Post

StackAdapt·Software Engineer·Technical Phone Screen

May 2026

Had a technical screen for a Software Engineer role at StackAdapt that leaned heavily into CS fundamentals. The question was about hash map internals and I had to think through more layers than I expected.

Analyze the time complexity of dictionary/hash map operations: specifically, what are the average-case and worst-case runtimes for key lookup, and how do factors like hashing quality, collision handling strategy, load factor, and resizing affect performance?
What is the time and space complexity of copying all keys from a hash map into a list, and what factors influence that cost including iteration, list allocation, and whether the map is ordered?

“I started with O(1) average and O(n) worst case which is correct, but then they kept pulling on the thread.”

View Post

StackAdapt·Software Engineer·Technical Phone Screen

May 2026

Coding round at StackAdapt for a software engineering role. One meaty design-plus-implementation question that took up the whole session, and it had more moving parts than it looked like at first glance.

Design and implement a time-windowed key-value store that only retains entries from the most recent window of N milliseconds. It needs to support Get(key), Put(key, value), and GetAverage() over valid entries, and you should discuss data structure choices and time complexity tradeoffs.

“I went straight to HashMap for the key-value lookup and thought I was done with the structure in two minutes.”

View Post

StackAdapt·Software Engineer·Technical Phone Screen

May 2026

Stackadapt software engineer interview that went deep into graph traversal and system design. One meaty problem, lots of follow-ups about edge cases I hadn't fully thought through.

You have a graph where nodes represent instances of two different entity types, and edges connect related entities across types. You're given two separate functions to fetch neighbors for each entity type. Implement a traversal that runs a validation function on every node in the graph. How do you handle cycles, disconnected components, and memory pressure on large graphs?

“I went straight to BFS and felt okay about it until they pushed on disconnected components.”

View Post

StackAdapt·Software Engineer·Technical Phone Screen

Apr 2026

Technical phone screen for a Software Engineer role at StackAdapt that went pretty deep on HashMap internals. Not a casual 'what's a hash table' conversation, they wanted you to actually reason through complexity tradeoffs and Java 8 specifics.

What is a hash collision and why does it happen?
Walk me through how put, get, and remove work in a HashMap at a high level.
What are the average and worst-case time complexities for HashMap operations, and what does Java 8 do to improve the worst case?
What happens if a key's hashCode changes after it's been inserted into a HashMap?
Why does resizing a HashMap improve performance?
What is the difference between HashMap and ConcurrentHashMap?

“Felt confident here.”

View Post

StackAdapt·Software Engineer·Onsite - System Design / Architecture

Apr 2026

System design round at Stackadapt for a software engineering role. The question was a multi-part thing that built on earlier validation work, and then asked you to tie it all together into an actual API design with a real discussion component. Pretty involved for a single question.

Using two validation functions you built earlier, design and write pseudocode for an update API for both classes. The API should accept an update payload, run the right validation, reject with all error messages if it fails, and apply the update atomically if it passes. Also discuss partial vs full update semantics, concurrency handling, and what the error response format should look like.

“This one was a lot.”

View Post