18 questions · from 5 interviews
HackerRank interview questions
Every question candidates reported from their HackerRank interviews, most frequently asked first. Each links to the write-up it came from, so you can see the round and how it went.
HackerRank coding and DSA questions
- 01
Tier-Aware Rate Limiter
Implement a tier‑aware rate limiter in Java. - Downstream service capacity: 80 requests per 5 seconds. - API input: tier (Enterprise, Pro, Free) and tenant (customer identifier). - Responses: return 200 when the request is allowed, 429 when rejected. -…
From HackerRank Senior Backend Engineer Interview Experience
- 02
Two Sum (HashMap variant)
Given an array of integers, find the indices of the two numbers such that they add up to a specific target. Use a hash map to achieve O(n) time complexity.
Easy · From Hackerrank | Backend Engineer 2 | Bangalore | Rejected
- 03
Permutation Divisible by 8
Given a list of strings, determine if any permutation of any string is divisible by 8. A number is divisible by 8 if its last three digits form a number divisible by 8, so only permutations of 3‑digit subsets need to be checked.
Medium · From Hackerrank | Backend Engineer 2 | Bangalore | Rejected
- 04
Binary Array with Prefix Balance and Optimal Subarray
Binary array problem involving prefix balance and optimal subarray length.
- 05
Binary Array with Limited Modification
Allowed a limited modification in the array to maximize the result.
- 06
Binary Array with Prefix Validity Constraints
More constraint-heavy variant focusing on prefix validity.
- 07
Log Processing for Suspicious Users
Log-processing problem to detect suspicious users based on transaction frequency.
- 08
Binary/String Manipulation with Tight Constraints
Binary / string manipulation problem with tight constraints.
- 09
Contiguous Array
Given a binary array nums, return the maximum length of a contiguous subarray with an equal number of 0 and 1.
Medium · From Hackerrank Backend Engineer II Interview Experience
- 10
Longest Subarray with at most one flip to make equal 0s and 1s
If you are allowed to flip atmost 1 value in the array i.e 0 to 1 or 1 to 0, calculate the longest subarray with an equal number of 0s and 1s.
- 11
Longest Subarray with all Prefixes having ones >= zeroes
Longest subarray with all prefixes of that subarray should have ones more than or equal to zeroes.
- 12
Suspicious User IDs from Transaction Logs
Given a log entries of the form "senderid receiverid transactionamount" (senderid, receiverid and transactionamount contain only digits), basically a vector of strings of the mentioned format and an integer "threshold", you have to return all the suspicious…
HackerRank system design questions
- 01
Design a Test‑Taking Platform
Design a platform similar to HackerRank where users can take coding tests. Focus on database schema design for codeStubs and testCases to allow highly optimal execution and storage.
- 02
Design a Rate Limiting / Notification System
Design a rate-limiting / notification-style system (API + core classes). Discussion included: Identifying entities and relationships Class design and responsibilities Hovering concurrency and edge cases Extensibility and trade-offs Interviewer focused on…
- 03
Design an Online Coding Assessment Platform
Design an online coding assessment platform (similar to HackerRank). Covered: Functional & non-functional requirements High-level architecture Core services and data models Code submission & evaluation flow Scalability and trade-offs Very collaborative and…
- 04
Design Hackerrank-like Online Coding Test Platform
Design a system similar to Hackerrank i.e Companies can create online coding tests and users can attend tests. Discuss functional and non-functional requirements, overall high level system design, database schema design, and the question submission flow (user…
- 05
Avoiding Containers in GitPod-like Development
Given a scenario of developing something similar to GitPod, how could one approach this while avoiding the use of containers?
Hard · From Hackerrank SWE Intern 2021
HackerRank behavioural and HR questions
- 01
Discussion on Open-Source Contributions
The interviewer asked about my past open-source contributions, specifically inquiring about which parts I contributed to and the implementation details of those contributions.
HackerRank interview questions FAQ
What questions are asked in HackerRank interviews?
Candidates reported 18 distinct questions across 5 HackerRank interviews. 12 coding and DSA questions, 5 system design questions, 1 behavioural and HR questions.