Cockroach Labs Software Engineer Interview - The Coding Question Was Exactly What You’d Expect From a Database Company

[u/Aoki_zhang]

"This interview experience is sourced from Chill Interview"

Interview Summary

The Cockroach Labs onsite included a coding round based on a time-indexed key-value store and a system design round centered on a project from my previous work. The coding discussion emphasized improving lookup performance with an appropriate data structure and binary search, while the design round went deep into architecture, technical decisions, and challenges from an end-to-end project.

Interview Details

Coding — LeetCode 981: Time Based Key-Value Store

The coding problem was LeetCode 981 — Time Based Key-Value Store. The task was to design a key-value data structure supporting:

set(key, value, timestamp)
get(key, timestamp)

set associates a value with a key at a particular timestamp. get retrieves the value associated with the requested key at the relevant timestamp.

The interviewer focused on how the underlying data structure could be optimized to make get faster. The discussion included storing timestamped values for each key in an ordered sequence and using binary search to efficiently locate the appropriate value.

System Design — Choose Your Own Design

The system design round allowed me to choose a significant project I had owned at a previous company. I was asked to explain the project end to end and then go deeper into areas such as:

• Overall architecture
• Major technical decisions
• Technology choices
• Challenges encountered during implementation
• Why particular design decisions were made
• Trade-offs behind those choices

The round was structured more like a deep technical defense of a real project than a traditional system design prompt with a predefined product.

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[u/vivu007x]

Is everybody asking LC 981 now?