Preparing for a Mobile Engineer interview at Grubhub requires a balanced approach that covers deep technical execution, architectural vision, and collaborative behaviors. You should approach your preparation with a clear understanding of the core competencies the engineering team evaluates.

Mobile Domain Expertise – You must possess a deep, platform-specific understanding of iOS or Android development. This includes knowing how the operating system manages memory, handles UI rendering pipelines, schedules background tasks, and optimizes network requests.

Architectural Thinking – You will be asked to design systems from scratch. You must show that you can structure a codebase for testability, scalability, and modularity, making conscious decisions about state management, local storage, and separation of concerns.

Test-Driven Mindset – Grubhub places a strong emphasis on code quality and Test-Driven Development (TDD). You should be comfortable writing unit tests, mocking network dependencies, and explaining how your design decisions facilitate automated testing.

Adaptability & Technology Alignment – You must demonstrate a highly collaborative, pragmatic attitude toward technology. Showing flexibility and an openness to working with legacy systems, hybrid technologies, or specific frameworks used by the team is crucial for passing the final management rounds.

The interview loop for a Mobile Engineer at Grubhub is structured to assess your technical depth, coding efficiency, and team compatibility. The process typically begins with an initial recruiter screen, where you will discuss your background, career goals, and general alignment with the role. If there is a mutual fit, you will move on to the technical screening phase, which may consist of a home-task assignment or a live technical phone screen with a senior mobile engineer focusing on platform-specific fundamentals and coding.

Once you pass the initial technical screen, you will progress to the final round interviews. This stage consists of multiple specialized sessions, typically lasting about an hour each. You will face a live coding and problem-solving challenge, a dedicated mobile system design session, and a behavioral interview with engineering managers and team leads. The final round is designed to be highly interactive, treating the candidate as a peer and focusing heavily on collaborative problem-solving.

The visual timeline above outlines the typical progression from the initial recruiter screen through to the final offer stage. Candidates should use this roadmap to pace their preparation, ensuring they allocate ample time to study platform design patterns before reaching the intensive final loop. While the exact ordering of the technical screens can occasionally vary based on the specific team and location, the core evaluation pillars remain highly consistent.

To stand out during the interview process, you must excel across several core technical and behavioral dimensions. Each of these areas is rigorously evaluated by different members of the Grubhub mobile team.

Mobile System Design

This area evaluates your ability to build production-grade mobile applications that can handle real-world constraints such as poor network connectivity, limited device memory, and high concurrency. Strong candidates do not just list technologies; they explain the trade-offs of their architectural choices.

Be ready to go over:

• UI Architecture Patterns – Deep understanding of MVVM, VIPER, or MVI, and how to manage view state cleanly.
• Data Synchronization & Caching – How to design an offline-first experience, handle local database migrations (Room, CoreData, or SQLite), and build efficient network caching.
• Image & Resource Management – Strategies for lazy loading, downsampling, memory caching, and disk caching of heavy assets.
• Advanced concepts (less common) – Multi-module project structures, dynamic feature delivery, and custom UI rendering pipelines.

Example scenarios:

• "Design the architecture for a real-time food delivery tracking screen that updates the driver's location on a map every few seconds."
• "Outline how you would build a highly performant restaurant menu screen with nested scrolling lists, dynamic price updates, and heavy image assets."

Test-Driven Development & Code Quality

Grubhub values robust, maintainable code. In this evaluation area, you will be asked to write code or solve problems while demonstrating a strong commitment to clean code principles and comprehensive testing.

Be ready to go over:

• Unit Testing Frameworks – Familiarity with JUnit, Mockito, XCTest, or equivalent mocking libraries.
• Writing Testable Code Dependency injection (e.g., Dagger, Hilt, or Swinject) and how it enables effective unit testing.
• Refactoring Techniques – How to identify code smells and refactor legacy code into a highly testable structure.

Example scenarios:

• "Given a piece of legacy network-calling code, refactor it to decouple the business logic from the framework and write a unit test for it."
• "Walk through a live coding exercise where you write the tests first (TDD) to implement a simple utility class."

Platform & Language Fundamentals

This section digs deep into the nuts and bolts of your primary platform. You cannot rely on high-level framework abstractions here; you must show that you understand how the underlying platform operates.

Be ready to go over:

• Threading & Concurrency – How to avoid blocking the main thread, dispatching background work, and handling race conditions.
• Memory Management – Detecting and fixing memory leaks, understanding strong/weak references, and using profiling tools like Instruments or LeakCanary.
• Custom Views & Layout Performance – How the layout pass works and how to optimize complex view hierarchies.

Example scenarios:

• "Explain what happens under the hood when a user scrolls rapidly through a list of complex views, and how you would prevent dropped frames."
• "Describe a scenario where a retain cycle or memory leak could occur in a reactive programming stream and how you would prevent it."

Technology Alignment & Collaboration

This evaluation area focuses on how you work within an engineering organization. Grubhub wants to ensure that you are open-minded, adaptable to their existing technology choices, and capable of working productively alongside QA, DevOps, and Product teams.

Be ready to go over:

• Cross-functional Collaboration – How you partner with QA to define test cases and work with backend engineers to design clean API contracts.
• Enthusiasm for the Tech Stack – Demonstrating a pragmatic approach to technology, showing that you value solving business problems over dogmatic framework preferences.
• CI/CD & Release Processes – Understanding of automated build pipelines, beta distribution (TestFlight, Firebase), and feature flagging.

Example scenarios:

• "Describe how you would handle a situation where the backend team cannot deliver an API contract on time, but your mobile feature is blocked."
• "How do you approach learning and adopting an internal framework or tool that is specific to your company?"