Engineering Program Manager, Apple Cloud Infrastructure, Apple Services Engineering

Apple

Let's explore the concept of containment. Imagine you're building a system for managing different types of electronic devices, such as smartphones, laptops, and tablets. Each device has specific properties and functionalities. You need a way to represent these devices and their relationships in a structured manner using object-oriented principles. Specifically, how would you use containment to model the 'has-a' relationship between a device and its components, such as a smartphone containing a camera, a screen, and a battery? Consider the following aspects in your design: Class Structure: How would you define the classes for Device, Smartphone, Camera, Screen, and Battery? Clearly demonstrate how these classes would interact with each other. Containment Implementation: Provide code snippets (in a language of your choice, such as Java, Python, or C++) to illustrate how you would implement containment to represent the 'has-a' relationship. Show how a Smartphone object would contain instances of Camera, Screen, and Battery objects. Benefits of Containment: Explain the advantages of using containment in this scenario. How does it promote code reusability, maintainability, and flexibility? Provide specific examples related to the device management system. Alternatives to Containment: Discuss other approaches to modeling relationships between objects, such as inheritance. What are the tradeoffs between containment and inheritance in this context? When might you choose one over the other? Real-World Implications: How does this concept of containment apply to other real-world scenarios or software design problems? Provide at least two examples beyond the device management system. For example, your Smartphone class might have member variables that are instances of the Camera, Screen, and Battery classes. This way, the Smartphone contains these components. Your explanation should cover how these components are created, accessed, and managed within the Smartphone class. The goal is to demonstrate a solid understanding of how containment works and its practical benefits in object-oriented design.

Apple

System Design Question: Designing a URL Shortening Service like TinyURL Let's design a URL shortening service like TinyURL. Consider the following: Functional Requirements: Given a long URL, the service should generate a shorter and unique alias. When users access the short URL, they should be redirected to the original long URL. The system should be highly available and reliable. Analytics: Track the number of times a short URL has been accessed. Non-Functional Requirements: The system should have low latency for URL redirection. Shortened URLs should be relatively short in length. The system should be able to handle a large number of URL shortening and redirection requests. Scalability: The system should be scalable to handle a growing number of URLs and users. Capacity Estimation & Constraints: Assume 100 million URLs are shortened per day. Assume 1 billion redirections per day. Assume a read/write ratio of 10:1 (redirections vs. shortening). Short URL length should be as short as possible (e.g., 7 characters). High-Level Design: Discuss the components involved (e.g., web servers, application servers, database). Explain the URL shortening and redirection process. Propose a suitable database (e.g., SQL or NoSQL). Detailed Design: How to generate unique short URLs? Discuss approaches like hash functions, base-62 encoding, or UUIDs. What are the tradeoffs of each approach in terms of collision probability, URL length, and performance? Explain the database schema for storing the mappings between short and long URLs. Detail the caching strategy to improve redirection performance. Where should the cache be placed (e.g., client-side, CDN, in-memory cache)? What cache eviction policy should be used? Scaling and Availability: How to scale the system to handle the expected load? Discuss techniques like load balancing, database sharding, and replication. How to ensure high availability? Discuss strategies like redundancy, failover mechanisms, and monitoring. Rate Limiting: Implement rate limiting to prevent abuse (e.g., a user shortening too many URLs in a short period of time). Discuss different rate-limiting algorithms (e.g., token bucket, leaky bucket). Walk through the design process, addressing each of these points. Explain any tradeoffs you make in your design decisions. Show examples of how different technologies or architectural choices impact system performance and scalability.

Apple

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