xAI Software Engineer interview questions

74 Software Engineers have shared notes from their xAI interviews, with the questions they were asked in each round. That is 86% of the 86 xAI interview notes on Screna AI.

74 Software Engineer interview notes

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.”

View Post

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.”

View Post

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.”

View Post

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.”

View Post

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.”

View Post

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.”

View Post

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.”

View Post

xAI·Software Engineer·Technical Phone Screen

Jun 2026
Screened for an AI-focused software engineering role at xAI. The technical screen was pretty much one big question about hallucination mitigation, but it branched into a bunch of follow-ups that exposed how shallow my initial answer was.
  • How would you prevent or significantly reduce hallucinations in an LLM-based system? Walk through causes and concrete mitigations across the full stack.
  • Your RAG system is still hallucinating even though you have retrieval in place. The model's answer contradicts the retrieved passages. What's going wrong and how do you fix it?
  • How would you build an automated evaluation pipeline to measure hallucination rate whenever the model or prompt changes, and what would you use as ground truth?
  • When should a model say 'I don't know,' and how do you actually get it to abstain reliably without making it refuse everything?
  • How do hallucination mitigations change when the system is an agent taking real actions like calling APIs or writing code, rather than just generating text?

“I jumped straight to RAG like it was a magic fix and the interviewer just waited.”

View Post

xAI·Software Engineer·Onsite - Coding / Algorithms

Jun 2026
xAI software engineer interview, coding round focused entirely on iterator design with stateful behavior. The problem sounds straightforward until you actually try to serialize mid-iteration state in a clean way.
  • Design and implement a stateful iterator over a sequence that supports saving a snapshot of its current position and restoring from that snapshot later, including after a process restart. The API should include next(), hasNext(), saveState(), and restoreFromState(snapshot).
  • Follow-up: how would you extend the iterator to support multiple independent consumers forking from the same saved state?

“The basic iterator was fine, took maybe five minutes.”

View Post

xAI·Software Engineer·Technical Phone Screen

Jun 2026
xAI technical screen, systems-level stuff, basically a deep dive into how processes and threads work and what can go wrong when you share memory between them. felt like they wanted to see if you actually understood the tradeoffs or just memorized definitions.
  • What is the difference between a process and a thread, and which parts of memory do they share versus keep private?
  • What are the main risks that come with shared memory across threads, and what techniques do you use to mitigate them?

“I started with the textbook answer (separate address spaces for processes, shared heap for threads within the same process) and that landed fine.”

View Post