# In-memory key-value store interview question

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Source: https://www.aced.io/questions/5822/implement-key-value-store
Source observed: 2026-11-04T22:42:56.707Z
Last checked: 2026-11-04T22:42:56.707+00:00
Indexed: 2026-11-05T22:10:51.284+00:00

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# Design and implement an in-memory key-value store

We provide this **Medium**-difficulty coding interview question for designing and implementing an in-memory key-value store that supports:

- `set` operations
- Transactional `begin` operations
- `commit` operations
- `abort` operations

## Question details

- **Category:** [Coding](https://www.aced.io/questions?type=coding)
- **Roles:** [Software Engineer](https://www.aced.io/questions?role=swe), [AI Engineer](https://www.aced.io/questions?role=ai-engineer)
- **Companies:** [xAI](https://www.aced.io/questions?company=x-ai), [OpenAI](https://www.aced.io/questions?company=openai)
- **Interview reports:** 4 interviews
- **Last asked:** 4 months ago, as displayed on the page
- **Saved by:** 6 users

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## Interview experience

One shared experience is available for [xAI](https://www.aced.io/experiences/x-ai-senior-software-engineer-interview-3c2a0d), from a Software Engineer at Senior / L5 level, recorded as “a year ago.” The candidate described the following process:

> I originally applied to a different xAI role, and an engineer on that team redirected me to the Senior Safety role after a quick intro call. From there I did a hiring manager screen, a practical technical phone screen, and then an onsite in Palo Alto with one coding round and one hybrid coding/system design round, plus a short follow-up call after. The actual questions were much more practical class-design problems than LeetCode, which matched a broader trend I was seeing, but xAI gave almost no useful prep and the process felt pretty ad hoc. The onsite was easily my least favorite one because the whole thing started with armed guards, bag checks, and escorting me around the building, and then one interviewer spent a bunch of the coding round on his phone. I got rejected afterward with a vague note about a shift in prioritization of open roles, so I still do not know whether the role actually changed or if that was just their way of saying no.

## Community answers

No answers have been contributed by the community yet.

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