xAI interview notes, page 2 of 9

Mid-sized

Most of these xAI write-ups come from Software Engineers (74), then Machine Learning Engineers (11) and Backend Engineers (1). The most reported rounds are the technical phone screen (52), the system design round (12), the behavioral / leadership round (6) and the onsite coding round (4).

86 interview notes · updated Jul 2026

xAI·Software Engineer·Technical Phone Screen

Apr 2026

Got a coding problem from xAI for a software engineer role that was basically implementing a radix tree (prefix-compressed trie) storing integer sequences. One meaty problem, no behavioral stuff, just pure data structure work.

Implement a RadixCache class that stores sequences of integers using a radix tree (prefix-compressed trie), supporting insert and a depth-first dump of the tree structure.

“This one took me a minute to even parse correctly.”

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xAI·Software Engineer·Technical Phone Screen

Apr 2026

Interviewed for a software engineering role at xAI and got hit with an LRU cache design question. Pretty classic but the O(1) constraint is where things get interesting and where I probably could've been sharper.

Design and implement an LRU cache data structure with get and put operations, both running in O(1) average time.

“I knew the answer involved a hashmap plus a doubly linked list but explaining WHY took me longer than it should have.”

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xAI·Software Engineer·Technical Phone Screen

Apr 2026

Xai software engineer interview that went deep on parallel algorithms. One question, but it had a lot of surface area and I don't think I covered all of it cleanly.

Hand-write a parallel sorting algorithm from scratch. Pick your approach (parallel merge sort, parallel quicksort, sample sort, etc.), implement it using threads or a thread pool, and walk through workload partitioning, how you combine results, synchronization costs, when parallelism actually pays off, and the work/span complexity.

“I went with parallel merge sort because I figured it was the safest bet to reason about cleanly.”

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xAI·Software Engineer·Technical Phone Screen

Apr 2026

Interview at xAI for a software engineer role, focused heavily on Rust internals and memory semantics. The questions went deeper than I expected for what I assumed would be a standard systems screen.

What is a string in programming languages, and how would you design and implement a string type from scratch in Rust, including what fields would live inside the struct?
What is the time complexity of copying a string, and how does that relate to how strings are laid out in memory?
How can move semantics be made more efficient compared to copying, and in Rust specifically, is a move just a reference update under the hood?

“Started okay with the high-level definition but the 'design it yourself' part is where I slowed down.”

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xAI·Software Engineer·Onsite - Coding / Algorithms

Apr 2026

Technical round for an ML Infra role at xAI. The whole thing was a coding exercise around distributed matrix multiplication, two strategies, and you had to actually implement both with a provided skeleton. More systems-flavored than pure algo, which I appreciated but also was not fully prepared for.

Complete the data parallel matrix multiplication function: each worker has a full copy of the weights and a shard of the input batch. Compute the local output per worker and assemble the final result correctly.
Implement fully sharded data parallel matrix multiplication from scratch: shard the weight matrix across workers, use an all-gather collective to retrieve needed shards at compute time, and keep per-worker memory bounded by the shard size.
Walk through the correctness guarantees, memory footprint, and communication overhead for each of the two parallelism strategies you implemented.

“This part felt more approachable.”

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xAI·Software Engineer·Technical Phone Screen

Apr 2026

xAI SWE interview that was basically one extended coding problem. They had me build an iterator class from scratch and then kept layering on requirements until it turned into something more interesting than I expected.

Implement an iterator class with next, hasNext, getState, and setState methods.
Extend your iterator to wrap a list of iterators and expose them as a single continuous sequence with a global index.

“The first two methods were fine, I've done iterator stuff before.”

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xAI·Software Engineer·Technical Phone Screen

Apr 2026

Interviewed for a software engineer role at xAI and got a recursive data structure problem. Pretty classic but the edge cases kept me on my toes longer than I expected.

Write a function that takes an arbitrarily nested Python data structure (which can contain lists, dicts, and tuples) with integer leaf values, and returns a flat list of all integers in the order they are encountered.

“I went straight for recursion, which was the right call, but I fumbled the dict case initially.”

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xAI·Software Engineer·Take-home Assignment

Apr 2026

Xai had me do a take-home style coding exercise where I had to build a small LLM API wrapper from scratch. The scope was bigger than I expected and the discussion afterward got pretty deep into design decisions.

Build a small library that calls an LLM API endpoint with configurable parameters like model, temperature, top_p, max_tokens, and stop sequences. It should handle retries with backoff, rate limiting, prompt batching, async and streaming responses, and structured logging.
Walk through your API design choices for the library and explain how you'd integrate it into a larger production application.
How did you approach error handling across the different failure modes, and what tradeoffs did you make?

“This was a lot more surface area than I budgeted time for.”

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xAI·Software Engineer·Recruiter / HR Screen

Apr 2026

Applied to xAI and got a question about motivation and fit. Pretty standard opener but it forced me to actually think about why I wanted to work there specifically.

Why do you want to work at xAI? Talk about what draws you to the mission and product, how your background fits the role, and what you'd specifically bring to the team.

“I had a rough draft answer in my head but saying it out loud felt a lot thinner than I expected.”

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xAI·Software Engineer·Hiring Manager Screen

Apr 2026

Interviewed at xAI for what seemed like a generalist ads-related product role. Just one question to go off of, but it was a career goals follow-up that required more prep than I gave it.

After your self-introduction, the interviewer asked: what do you plan to do next? Walk through your near-term career goals, the types of problems you want to tackle, and why this generalist ads-related role specifically fits where you want to go.

“I fumbled this more than I expected.”

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