1. What is a Mobile Engineer?

As a Mobile Engineer at OpenAI, you are the bridge between our cutting-edge research and the hands of millions of users worldwide. While our models reside in the cloud, the mobile experience—whether on iOS or Android—is often the primary interface through which the world interacts with ChatGPT and our future AI-native applications.

This role goes beyond standard application development. You are tasked with crafting seamless, low-latency, and highly responsive interfaces that make complex AI interactions feel magical and instantaneous. You will work within the Applications Engineering organization, collaborating closely with design, product, and research teams to translate raw model capabilities into intuitive mobile features. Your work directly impacts how humanity experiences the benefits of AGI, requiring a focus on performance, accessibility, and reliability at a massive global scale.

2. Getting Ready for Your Interviews

Preparing for an interview at OpenAI requires a shift in mindset. We look for engineers who are not just proficient coders but also thoughtful product builders. You should approach your preparation with the goal of demonstrating how you build robust, user-centric systems.

We evaluate candidates based on several key criteria:

Technical Proficiency & Craftsmanship You must demonstrate deep fluency in your platform’s native ecosystem (Swift/iOS or Kotlin/Android). We evaluate your ability to write clean, maintainable, and idiomatic code that leverages the latest platform capabilities while maintaining backward compatibility and performance.

System Design & Architecture We assess how you structure complex mobile applications. You should be able to discuss architectural patterns (MVVM, MVI, TCA), data management, offline capabilities, and how to handle network-heavy operations—specifically streaming data, which is central to the ChatGPT experience.

Product Sense & User Focus OpenAI engineers are expected to care deeply about the user experience. We evaluate your ability to make trade-offs between engineering complexity and user value. You should be prepared to discuss how you measure performance (latency, frame rates) and how you ensure the application feels responsive.

Culture Alignment & Mission We look for individuals who are collaborative, humble, and aligned with our mission to ensure AGI benefits all of humanity. You will be evaluated on your ability to navigate ambiguity, work cross-functionally, and prioritize safety and security in your engineering decisions.

3. Interview Process Overview

The interview process for the Mobile Engineer role is designed to be rigorous yet practical, reflecting the actual work you will do on the team. Generally, the process moves efficiently, often taking about 4 weeks from initial contact to final decision. We prioritize a holistic view of your skills, combining traditional technical assessments with practical, domain-specific challenges.

You can expect to start with a recruiter screen to align on your background and interests, followed by a technical screen. This screen typically involves a practical coding task that focuses on mobile fundamentals rather than abstract algorithmic puzzles. If you advance, you will proceed to the onsite stage (often virtual), which consists of a series of interviews covering coding, system design, and behavioral alignment. Our process is known for being thorough; we want to ensure you are set up for success in a high-impact environment.

The timeline above illustrates the typical flow for a Mobile Engineering candidate. Use this to plan your preparation: early stages focus on raw coding ability and platform knowledge, while the later stages require you to synthesize your technical skills with architectural thinking and cultural fit. Be prepared for a mix of live coding (often in an IDE) and whiteboard-style design discussions.

4. Deep Dive into Evaluation Areas

To succeed, you must demonstrate expertise across specific technical and non-technical domains. Based on the expectations for this role, we have structured the evaluation into the following core areas.

Practical Mobile Coding

This is the cornerstone of the technical evaluation. Unlike generic coding interviews, our mobile coding rounds often simulate real-world feature development. You may be asked to implement a specific UI component, handle a network request, or debug a performance issue.

Be ready to go over:

• Concurrency & Threading – Managing background tasks, avoiding main thread blocks, and handling race conditions (GCD/Actors for iOS, Coroutines/Flow for Android).
• UI Implementation – Building complex layouts programmatically or via declarative frameworks (SwiftUI/Jetpack Compose) with a focus on pixel-perfect implementation.
• Networking – Handling API responses, specifically streaming responses (Server-Sent Events), which are critical for LLM interactions.
• Advanced concepts – Custom transitions, haptics integration, and accessibility standards.

Example questions or scenarios:

• "Build a chat interface that fetches messages from an API and handles pagination."
• "Implement a search feature that debounces user input and caches results locally."
• "Refactor a piece of code that causes a memory leak due to retain cycles."

Mobile System Design

In these rounds, we evaluate your ability to architect scalable mobile applications. You will be presented with a high-level problem and asked to design the client-side architecture.

Be ready to go over:

• Data Layer Architecture – Designing repositories, caching strategies, and offline-first synchronization.
• State Management – How you handle global vs. local state and ensure UI consistency across screens.
• Performance Optimization – Strategies for reducing app size, optimizing battery usage, and minimizing network latency.
• Advanced concepts – Modularization, dependency injection at scale, and security best practices for storing sensitive tokens.

Example questions or scenarios:

• "Design the architecture for a real-time voice assistant app."
• "How would you design an image loading library from scratch?"
• "Design a system to handle real-time updates for a collaborative document editor on mobile."

Behavioral & Cross-Functional Collaboration

We value engineers who can lead initiatives and work well with others. These interviews focus on your past experiences and how you handle challenges.

Be ready to go over:

• Conflict Resolution – How you resolve technical disagreements with peers or product managers.
• Ambiguity – Examples of how you moved a project forward when requirements were unclear.
• Ownership – Times you took responsibility for a failure or drove a project from conception to launch.

The word cloud above highlights the most frequently discussed topics in our mobile interviews. Notice the heavy emphasis on Concurrency, Architecture, UI/UX, and Streaming. Prioritize your study time to ensure you can speak confidently and in-depth about these specific technical areas.

5. Key Responsibilities

As a Mobile Engineer at OpenAI, your daily work is centered on building and refining the flagship ChatGPT experience. You will be responsible for implementing new features that showcase the power of our AI models, often working with experimental capabilities that have never been deployed on mobile before.

You will collaborate intimately with backend engineers to define API contracts that support low-latency streaming and real-time updates. A significant portion of your time will be spent optimizing app performance; given the computational cost of AI, the mobile client must be highly efficient to ensure a responsive user experience. Additionally, you will establish robust testing frameworks to prevent regressions and ensure that our rapid release cadence does not compromise stability. You are expected to provide technical leadership, helping to shape the long-term roadmap of our iOS or Android platforms.

6. Role Requirements & Qualifications

We are looking for engineers who have a proven track record of shipping high-quality mobile software.

• Technical Skills:

  • iOS: Fluency in Swift, deep knowledge of UIKit and SwiftUI, and familiarity with Xcode instruments for profiling.
  • Android: Fluency in Kotlin (Java knowledge is a plus), expertise in Jetpack Compose, Coroutines, and modern Android architecture components.
  • General: Strong grasp of computer science fundamentals (data structures, algorithms) and mobile networking (REST, WebSockets, SSE).

• Experience Level:

  • Typically 6+ years of professional software engineering experience.
  • A portfolio of apps released in the App Store or Play Store.
  • Experience working in cross-functional teams (Product, Design, Backend).

• Soft Skills:

  • Ability to communicate complex technical constraints to non-technical stakeholders.
  • A proactive approach to problem-solving and a willingness to learn new technologies quickly.

• Nice-to-have vs. Must-have:

  • Must-have: Deep native platform knowledge and experience with modern concurrency models.
  • Nice-to-have: Experience with C++ (for shared logic), voice/audio processing, or integrating on-device ML models (CoreML/TFLite).

7. Common Interview Questions

The following questions are representative of what you might encounter. They are not an exact script but are designed to help you recognize the types of challenges we present. We often use practical, open-ended questions to see how you approach problems in real-time.

Technical & Coding

These questions test your raw coding ability and familiarity with platform APIs.

• "Implement a function to download images asynchronously and display them in a list, ensuring no flickering during scrolling."
• "How would you implement a thread-safe counter in Swift/Kotlin?"
• "Write a view component that animates a streaming text response (typewriter effect) efficiently."
• "Detect and fix a retain cycle in the provided code snippet."

System Design

These questions assess your ability to think big and structure complex systems.

• "Design a mobile client for a social media feed. How do you handle caching, pagination, and offline viewing?"
• "How would you architect a mobile app that relies heavily on WebSocket connections for real-time data?"
• "Design the networking layer for an app that needs to prioritize battery life and minimize data usage."

Behavioral & Situational

These questions evaluate your fit with our culture and working style.

• "Tell me about a time you had to optimize a piece of code that was causing performance issues in production."
• "Describe a situation where you had to push back on a product requirement because of technical feasibility."
• "How do you stay up to date with the latest changes in the iOS/Android ecosystem?"

These questions are based on real interview experiences from candidates who interviewed at this company. You can practice answering them interactively on Dataford to better prepare for your interview.

8. Frequently Asked Questions

Q: How much does OpenAI focus on LeetCode-style algorithms versus practical mobile tasks? While you should be comfortable with fundamental algorithms, our process leans heavily toward practical application. We prefer questions that mirror the actual work of a mobile engineer, such as building UI or managing data flows, over abstract puzzles.

Q: Is this role remote or onsite? The Mobile Engineering roles are primarily based in our San Francisco office. We believe in the value of in-person collaboration for our creative and fast-paced work environment, though we offer hybrid flexibility.

Q: What is the most common reason candidates fail the technical rounds? Candidates often struggle with concurrency and state management. Make sure you understand how your platform handles background threads and how to update the UI safely and efficiently without race conditions.

Q: How should I prepare for the "System Design" round if I haven't done one before? Focus on standard mobile patterns. Practice sketching out the architecture for popular apps (like Instagram, WhatsApp, or ChatGPT). Be explicit about your choices regarding database usage, network protocols, and modularization.

9. Other General Tips

• Master the "Why OpenAI?" Question: Be ready to articulate a genuine passion for our mission. We want to know why you want to build here specifically, not just why you want a job in tech. Connect your personal drive to our product impact.
• Think "Streaming" First: Unlike many apps that wait for a full payload, our products rely on streaming text. Understand how Server-Sent Events (SSE) work and how to handle them gracefully on a mobile client.
• Focus on Polish: In the practical coding rounds, don't just make it work; make it feel good. Small details like smooth animations, proper error states, and loading indicators matter significantly.

• Review Your Basics: Don't let simple things trip you up. Review view lifecycles (UIViewController/Activity), memory management (ARC/Garbage Collection), and basic networking setups before your interview.

10. Summary & Next Steps

Becoming a Mobile Engineer at OpenAI is an opportunity to define the interface of the AI era. You will be working on products that are reshaping how the world interacts with information, creativity, and productivity. The work is challenging, fast-paced, and incredibly high-impact.

The compensation data above reflects the competitive nature of this role. At OpenAI, we value top-tier talent and structure our offers to include significant equity upside, aligning your success with the company's long-term mission.

To succeed, focus your preparation on native platform mastery, concurrency, and mobile system design. Review the topics in this guide, practice building small apps that handle streaming data, and come ready to discuss how you build for the user. We are looking for builders who are ready to push the boundaries of what mobile devices can do with AI.

Good luck with your preparation. We look forward to seeing what you can build.