HackTheRounds Interview Experiences

xAI Software Engineer Interview Experience (2026): Phone Screen to Onsite, Full Process

xAI's fast paced SWE interview: 15 minute phone screen, Trie/DFS word search, LRU cache implementation, and in memory database system design.

By Anonymous · 2026-03-05

Background

I'm a new grad who wasn't actively looking at xAI, but their recruiter reached out to me directly. The process was noticeably faster and less structured than Big Tech — it felt more like a startup interview, which makes sense given how young the company is.

Phone Screen (15 minutes)

This was unlike any phone screen I've done. It was rapid-fire "quick question, quick answer" with barely any room to elaborate:

I was caught off guard by the pace. Before I knew it, the call was over and I was told I'd be moving to the onsite. No coding at all in this round.

Onsite Round 1: Word Search (Trie + DFS)

Given a letter grid and a list of words, find all words that can be formed by traversing adjacent cells. Essentially a harder version of Boggle / Word Search II.

I built a Trie from the word list, then ran DFS from each cell with backtracking. The key optimization was pruning branches of the Trie as words were found to avoid redundant searches. The interviewer cared a lot about edge cases — what about single-letter words? What about the same cell being visited twice?

Onsite Round 2: LRU Cache

Implement an LRU Cache with O(1) get and put operations. Standard hash map + doubly-linked list approach.

I got tripped up briefly on updating the tail pointer when removing the least recently used item — caught it while self-testing my solution. The interviewer was patient and let me debug on my own rather than giving hints.

Onsite Round 3: System Design — In-Memory Database

Design an in-memory database that supports nested transactions: - SET key value - GET key - BEGIN (start transaction) - ROLLBACK (undo current transaction) - COMMIT (apply current transaction)

Transactions can be nested — a BEGIN inside a BEGIN creates a savepoint.

I used a stack of hash maps where each BEGIN pushes a new layer. GET searches down the stack. COMMIT merges the top layer into the one below. ROLLBACK pops the top layer.

The interviewer then asked me to extend it with: - Write-ahead logging for durability - Snapshot isolation for concurrent reads - How would you distribute this across multiple machines?

This round felt very open-ended — they wanted to see "flexible thinking" rather than one correct answer.

Tips

  1. The phone screen is a formality — just don't say anything disqualifying. The real evaluation is the onsite
  2. Cover LeetCode staples — Word Search II, LRU Cache, and system design patterns are high-frequency
  3. Test your own code — they let you find your own bugs rather than hinting. Self-testing is expected
  4. System design is open-ended — there's no single right answer. Show breadth of thinking (concurrency, durability, distribution)
  5. Fast process — expect to go from phone screen to onsite within a week or two