xAI

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

Jul 2026

xAI software engineer technical screen, one coding problem the whole time. Classic phone keypad encoding thing, looked familiar but the trie angle tripped me up a bit.

Given a dictionary of words and a list of digit-string queries, return all dictionary words whose phone keypad encoding starts with each query, sorted lexicographically. Each digit 2-9 maps to a group of letters the way old T9 phones worked.

“My first instinct was to just encode every word upfront and then for each query do a prefix scan.”

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xAI·Software Engineer·Online Assessment (OA)

Jul 2026

xAI SWE interview had me building an in-memory database from scratch across four progressive levels, starting with basic CRUD and ending with TTL expiry and backup/restore logic. It was a single coding round and the problem kept stacking requirements on top of itself, which was the whole point.

Implement basic CRUD operations (set, get, delete) on fields within keyed records in an in-memory database.
Add scan and scan-by-prefix operations that return all fields (or prefix-matching fields) for a given key, formatted as 'field(value)' and sorted lexicographically.
Extend the database with timestamped versions of all operations, including a set_at_with_ttl that makes a field expire at timestamp + ttl (half-open interval).
Implement backup and restore: backup captures a snapshot at a given timestamp (storing remaining TTL for fields), and restore reinstates the latest backup at or before a target time, recalculating expiry relative to the restore timestamp.

“This part was fine.”

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xAI·Machine Learning Engineer·Technical Phone Screen

Jul 2026

Interviewed for an ML Engineer role at xAI and got a pretty deep systems-level coding question about building a batched inference engine from scratch. Not your typical LeetCode session, more like a mini-project scoped to an hour.

Design and implement a dynamic batching decoding engine for a black-box language model interface. The engine should manage a fixed-capacity batch, pull from a waiting queue to fill open slots, handle per-sequence stopping conditions (both a single stop token and a stop sequence suffix), respect per-request token limits, and correctly map batch slots to requests so outputs never get mixed up when slots are refilled.

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

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xAI·Software Engineer·Recruiter / HR Screen

Jun 2026

Screened for a software engineer role at xAI and the conversation zeroed in pretty quickly on motivation and fit rather than pure technical stuff. One question in particular required some real prep to answer well.

What specifically do you want to work on at xAI, and why? Walk us through which teams or projects interest you, how that connects to the company's mission, and why your background makes you a good fit.

“This tripped me up more than I expected.”

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xAI·Software Engineer·Technical Phone Screen

Jun 2026

Interviewed for a software engineer role at xAI. Pretty standard intro round, just one question but it was open enough that you could sink or swim depending on what project you picked.

Walk me through your background, then describe the most interesting project you've worked on. Make sure it's relevant to what this team does, and cover what made it interesting, what you personally did, and what the outcome was.

“The open-endedness of this tripped me up a bit.”

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xAI·Software Engineer·Hiring Manager Screen

Jun 2026

Behavioral round at xAI that was basically a rapid-fire interrogation of your resume. The interviewer zeroed in on your best project and just kept drilling. Fast paced and a bit relentless.

Walk me through your most impressive project. What was the problem you were solving?
Why is this project technically impressive? What makes it stand out?
What specifically did you contribute versus the rest of the team?
What were the key technical decisions you made, and what trade-offs did you consider?
Looking back, what would you do differently on that project?
What was the measurable impact of your work on this project?

“You really need to have one project locked and loaded before this conversation.”

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xAI·Software Engineer·Technical Phone Screen

Jun 2026

xAI software engineering interview with a thread safety debugging question. Pretty focused technical session, one meaty problem and a lot of follow-up probing around the edges.

You have a BankAccount class used by multiple threads simultaneously. Two deposits are submitted concurrently via a thread pool. Given the deposit implementation reads the balance, sleeps briefly, then writes back, explain why the final balance can be wrong, identify the concurrency bug, propose a thread-safe fix, and discuss any trade-offs or alternative approaches.

“I spotted the race condition pretty fast, the read-modify-write gap with the sleep in between is basically a neon sign.”

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xAI·Machine Learning Engineer·Technical Phone Screen

Jun 2026

Interviewed for an ML Engineer role at xAI and got hit with a pretty deep systems question about concurrency. Not the most ML-specific thing I expected but it makes sense given the infrastructure work they do.

Walk me through the differences between multiprocessing and multithreading for building concurrent applications, covering memory isolation, communication patterns, performance trade-offs for CPU vs I/O workloads, and failure containment. Give examples of when you'd actually pick one over the other.

“This was broader than I expected.”

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xAI·Software Engineer·Technical Phone Screen

Jun 2026

Interviewed for a software engineer role at xAI and got a pretty deep dive into arrays, way more than I expected for what I thought would be a warmup question.

What is an array, how is it laid out in memory, and what are the time complexities for access, insertion, and deletion? Also, what are the cache locality implications of that memory layout?

“Started fine, explained contiguous memory and index arithmetic (base + i * element_size), but then they pushed on alignment and I fumbled a bit.”

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xAI·Backend Engineer·Technical Phone Screen

Jun 2026

Did a coding round for a Backend Engineer role at xAI centered entirely on designing an in-memory database from scratch. Four levels of increasing complexity, each one adding something that made the previous solution feel underbuilt. Rough but interesting problem.

Implement basic get, set, and delete operations for an in-memory key-value store where each key holds multiple field-value pairs.
Add scan and scan_by_prefix operations that return all fields for a key sorted lexicographically, formatted as field(value) strings.
Extend all operations to accept an explicit timestamp, and add a set operation that assigns a TTL so fields expire after a given interval.
Implement backup and restore functionality: backup saves the full database state at a given timestamp including remaining TTLs, and restore rolls back to the most recent backup at or before a specified time while correctly recalculating TTL expiration.

“Felt straightforward at first.”

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xAI interview FAQ

What rounds are in the xAI interview?

Candidates most often report a technical phone screen (52 write-ups), a system design round (12), a behavioral / leadership round (6) and an onsite coding round (4).

What does the xAI technical phone screen cover?

Across 52 technical phone screen write-ups, the most tagged question topics are Technical Trade-offs (73 questions), System Design (61) and Algorithms & Data Structures (49).

What is asked in the xAI system design round?

Across 12 system design write-ups, the most tagged question topics are System Design (34 questions), Technical Trade-offs (30) and API & Integrations (5).