Rubrik onsite interview experience: Queue design using array
Question Details
Problem Statement Design a system to implement two queues within a single fixed-size array of length $N$. External data structures are permitted for metadata management, but all actual data elemen
Full Details
Problem Statement Design a system to implement two queues within a single fixed-size array of length $N$. External data structures are permitted for metadata management, but all actual data elements must be stored within the array. The primary challenge is efficient space reclamation: space freed by pop operations must be immediately available for reuse by either queue to prevent fragmentation and exhaustion of the array.
Proposed Solution Implement a block-based allocation strategy (similar to an Unrolled Linked List) to manage array segments dynamically. 1. Array Partitioning * Divide the physical array into $K$ fixed-size blocks. * Each block has a capacity of $N/K$ values. * Each block is defined by a LinkedListNode containing metadata: start_index, end_index, and pointers to adjacent nodes. 2. Metadata Structure * Use a Doubly Linked List (DLL) to maintain the logical order of blocks for each queue and the pool of free space. *
Queue Pointers: Maintain head1 and head2 pointers to track the start of the linked list for Queue 1 and Queue 2, respectively. *
Free Block Management: Maintain a tail or free_list pointer that links to a chain of currently empty blocks. 3. Operational Logic *
Push Operation: When a queue needs to store data, it writes to its current tail block. If the current block is full, an empty block is detached from the free_list and linked to the end of that queue. *
Pop Operation: Elements are removed from the block pointed to by the queue's head. When a block becomes completely empty after a pop operation, it is unlinked from the queue and moved back to the free_list to be reused by either queue.
About This Question
This is a reported interview question from a rubrik interview for a swe role during the onsite round reported in 2025.
It covers the following topics: Arrays, Linked List, System Design, Queue, Stack .
Topics
More Rubrik Interview Questions
About Rubrik Interview Reports
This question was reported by a candidate who interviewed at Rubrik. LeakCode aggregates interview reports from 10+ sources, including 1Point3Acres, Glassdoor, LeetCode Discuss, Blind, Reddit, Indeed, and Nowcoder. Each report is translated where necessary, deduplicated against existing entries, and tagged by company, role, round type, and reporting date.
Use this question as one calibration data point, not a memorization target. Companies typically rotate their question pools every 2-4 months; the exact wording of a 2024 question may differ from what you encounter today. The underlying pattern, difficulty level, and follow-up depth at Rubrik are the higher-signal extractions to take from this report.
For broader preparation context, the Rubrik interview process typically includes a recruiter screen, one or two technical phone screens, and a 4-5 round on-site loop covering coding, system design (at L4+ levels), and behavioral. Reports tagged on LeakCode show the round-by-round distribution and typical difficulty calibration. To browse questions filtered by round type and seniority, use the company hub linked above.
How To Practice This Type of Question
Solve similar problems on LeetCode under timed conditions (25-35 minutes per medium difficulty). The goal is pattern recognition: recognize the underlying technique (sliding window, two-pointer, BFS, memoized recursion, etc.) within 60-90 seconds of reading. Strong candidates verbalize their hypothesis out loud before coding, then iterate based on feedback. Weak candidates dive into implementation immediately, lose time on the wrong approach, and run out of time for follow-ups.
Companies update their question pools every 2-4 months. The exact wording of any given question may have been retired by the time you interview. Focus your prep on the pattern, not the specific problem. The patterns that appear in Rubrik reports consistently are the ones worth investing in; one-off niche problems are not.
During Your Rubrik Round
Apply the standard interview round template: clarify requirements (2-3 minutes), state your approach out loud and confirm direction with the interviewer (3-5 minutes), code with narration (15-25 minutes), test with concrete examples including edge cases (5 minutes), discuss optimization or trade-offs if time permits (5 minutes). This template is universally accepted across FAANG and adjacent companies; deviating from it produces weaker interviewer feedback signal.
The single most predictive failure mode in Rubrik reports tagged "no hire": not asking clarifying questions. Interviewers are explicitly trained to weight this. Strong candidates ask 3-5 clarifying questions even on problems that look obvious; weak candidates dive into code immediately. The clarifying-question check is often the first signal recorded in the interviewer's written notes.