OpenAI

OpenAI

Leading AI research laboratory developing state-of-the-art foundation models like GPT-4.

5 Rounds ~21 Days Very Hard
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The Interview Loop

Recruiter Screen (30 min)

Standard fit check, behavioral questions, and resume overview.

Technical Loop (3-4 Rounds)

Deep dive into domain knowledge, coding, and system design.

Interview Question Bank

Backend Engineer • Coding • easy

Given an array of API request start and end times, calculate the maximum number of concurrent requests the server handled.

#Arrays #Sorting #Sweep Line
Practice
Backend Engineer • Coding • medium

Implement a token bucket rate limiter that can handle both requests-per-minute and tokens-per-minute limits simultaneously.

#Concurrency #Data Structures #Rate Limiting
Practice
Backend Engineer • Coding • medium

Write a function to merge K sorted streams of tokens into a single sorted stream. Assume the streams are coming from different backend model replicas.

#Heaps #Streaming Data #Pointers
Practice
Backend Engineer • Coding • medium

Implement a thread-safe LRU Cache with a Time-To-Live (TTL) for each entry. This would be used to cache recent prompt embeddings.

#Hash Maps #Linked Lists #Concurrency
Practice
Backend Engineer • Coding • hard

Given a stream of nested JSON chunks (which may be fragmented), write a parser that yields valid JSON objects as soon as they are fully formed.

#String Manipulation #Parsing #Stacks
Practice
Backend Engineer • Coding • medium

Implement a Trie data structure optimized for fast prefix matching to detect blocked keywords in a streaming prompt.

#Trees #Trie #String Matching
Practice
Backend Engineer • Coding • hard

Serialize and deserialize an N-ary tree. This is used to represent branched conversation threads where users edit previous prompts.

#Trees #Serialization #DFS/BFS
Practice
Backend Engineer • Coding • hard

Implement a text justification algorithm. Given an array of words and a maximum width, format the text such that each line has exactly the maximum width.

#String Manipulation #Greedy Algorithms
Practice
Backend Engineer • Coding • medium

Find the longest substring with at most K distinct characters. (Used to optimize context window parsing).

#Sliding Window #Hash Maps #Strings
Practice
Backend Engineer • Coding • hard

Implement a distributed task queue executor. You have a central queue and multiple worker nodes. Ensure tasks are executed exactly once.

#Distributed Systems #Concurrency #State Machines
Practice
Backend Engineer • Coding • medium

Write a program to resolve dependencies for a set of AI agents. Given a list of agents and their dependencies, output a valid execution order.

#Graphs #Topological Sort #BFS/DFS
Practice

Difficulty Radar

Based on recent AI-sourced data.

Meet Your Interviewers

The "Standard" Interviewer

Senior Engineer

Focuses on core competencies, system constraints, and clear communication.

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Unwritten Rules

Think Out Loud

Always explain your thought process before writing code or drawing architecture.

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