Technical case: If you were to create Google Local Offers (which interviewer described as an app that sends push notifications for discounts for stores when you are close to them), what technical components do you need? What is the workflow, what would you need to store on the phone local storage? What interfaces would you need and what do they look like? What risks do you run into?

Building Google Local Offers: Technical Components and Workflow

Google Local Offers requires a location-aware mobile app, a robust backend system for offer management, and a real-time push notification service. Key components include GPS integration, local storage for caching, RESTful APIs for data exchange, and a scalable database for storing user preferences and offer details.

Introduction

The challenge of creating Google Local Offers involves developing a location-based service that delivers timely, relevant discounts to users based on their proximity to stores. This requires seamless integration of various technical components to ensure real-time responsiveness, data accuracy, and a smooth user experience. Our approach will focus on building a scalable architecture that can handle high volumes of location data and push notifications while maintaining performance and user privacy.

Step 1

Clarify the Technical Requirements (3-4 minutes)

• Looking at the system's core functionality, I'm considering a hybrid app architecture to leverage native device capabilities for location services. Could you confirm if there are any specific platform constraints or if we're targeting both iOS and Android equally?

Why it matters: Determines the development approach and potential code reuse. Expected answer: Target both platforms with equal priority. Impact on approach: Would consider using React Native or Flutter for cross-platform development.

• Considering the real-time nature of the offers, I'm thinking about using a pub/sub model for push notifications. Are there any existing messaging systems in place, or should we plan to implement this from scratch?

Why it matters: Affects the scalability and reliability of our notification system. Expected answer: No existing system, need to implement new. Impact on approach: Would need to evaluate cloud messaging services like Firebase Cloud Messaging or Amazon SNS.

• Regarding data storage, I'm assuming we'll need a distributed database to handle high read/write loads for offer management. Are there any specific data residency or compliance requirements we need to consider?

Why it matters: Influences our choice of database technology and hosting solutions. Expected answer: Data must be stored within specific geographic regions. Impact on approach: Would consider using a geo-distributed database like Google Cloud Spanner or Amazon Aurora Global Database.

• For the location tracking feature, I'm considering using geofencing to optimize battery usage. Are there any specific accuracy requirements or limitations we should be aware of?

Why it matters: Balances user experience with technical performance. Expected answer: Accuracy within 50 meters is sufficient. Impact on approach: Would implement a combination of GPS and network-based location services with adaptive polling.

Assumptions:

• We'll be developing for both iOS and Android platforms.
• We need to implement a new push notification system.
• Data storage must comply with regional regulations.
• Location accuracy within 50 meters is acceptable.