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Cursor interview notes, page 2 of 2

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Screna has 14 Cursor interview write-ups. The most reported round is the technical phone screen (9).

14 interview notes · updated Jul 2026

Cursor·Software Engineer·Onsite - System Design / Architecture

Jun 2026
System design round at Cursor for a software engineer role. The whole session was basically one big deep dive into building a transactional key-value store from scratch, with a lot of follow-up pressure on concurrency edge cases.
  • Design an in-memory key-value database that supports transactional reads and writes, exposing begin, get, set, commit, and rollback operations.
  • How does your design handle two transactions that concurrently write to the same key?
  • How would you handle a read-write race where two transactions read stale values and then swap those values between two keys?
  • What isolation level should transactions provide, and what are the trade-offs between serializable isolation, snapshot isolation, and weaker guarantees?
  • How would you support reads outside of any transaction context?
  • How would you prevent long-running transactions from making commit validation increasingly expensive over time?
  • How would you write a test to reliably reproduce the two-key swap race condition?
  • What changes would be needed to make this database durable?

“I started with a simple map and a per-transaction write buffer, which felt right, but I underestimated how quickly the interviewer would push on isolation.”

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Cursor·Software Engineer·Technical Phone Screen

Jun 2026
Cursor SE interview had me implementing a Merkle tree from scratch, which sounds manageable until you're actually doing it under pressure. Pretty technical round, no fluff.
  • Implement a Merkle tree from a list of data blocks, supporting root hash exposure, inclusion proof generation, and proof verification without the full tree. Also discuss time complexity and real-world applications.

“This was the whole interview basically.”

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Cursor·Software Engineer·Technical Phone Screen

Jun 2026
Cursor software engineering interview that threw a streaming parser problem at me. The core task was building something that could handle incremental text input and correctly identify inline code spans versus fenced code blocks, even when the delimiters get split across chunk boundaries. Pretty niche problem and I wasn't fully prepared for how stateful the solution needed to be.
  • Build a streaming Markdown parser that handles inline code spans (single backtick) and fenced code blocks (triple backtick), where input arrives in arbitrary chunk sizes and delimiters can be split across chunk boundaries.
  • Should unterminated code spans at the end of the stream be emitted as plain text or held in a buffer indefinitely?
  • How would you extend the parser to support tilde characters as an alternate fence marker?
  • How would you prevent the parser from buffering an unbounded amount of text while waiting for a closing delimiter?
  • How would you make the parser resumable if the process restarts mid-stream?

“This one hurt a little.”

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Cursor·Backend Engineer·Onsite - System Design / Architecture

Jul 2026
System design round at Cursor for a backend role. The whole thing was basically one big question about rate limiting across a user/team/company hierarchy, then a bunch of follow-ups that went pretty deep into distributed systems territory. Left feeling okay about the core design but less confident on some of the edge cases they pushed on.
  • Design a production-grade rate limiter for notification sending that enforces per-user, per-team, and per-company limits simultaneously within an exact rolling 10-minute window. A send is only accepted if all three limits pass, and a rejection must not count against any scope.
  • How do you keep the user, team, and company rate limit checks atomic across concurrent requests from many stateless servers?
  • What clarifying questions would you ask before designing this system?
  • How do you handle the user-to-team-to-company mapping, and what happens when a user is transferred to a different team mid-operation?
  • If the limits were changed from 3/10/20 to thousands per window, would you still use an exact sliding window log, and what would you switch to if not?
  • One large company's traffic is making its shard a bottleneck. How do you relieve the hot shard while still enforcing the exact company-level limit?
  • Walk through what happens end-to-end when the Redis cluster is briefly unavailable. What does your service return, what gets logged, and how do counts reconcile when it comes back?
  • How would you add a fourth rate limiting scope, like a per-notification-channel limit, without rewriting the atomic core of the system?

“This was the core question and it ate most of the session.”

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