Design a scalable game app store

You are asked to design a backend system for a **game app store**. The product is similar in spirit to an app marketplace but focused on games. ### Requirements #### 1. Browsing and discovery Users should be able to browse games via different types of categories: - **Dynamic categories** (computed from data): - Top-selling games (e.g., by recent purchase volume) - New releases (e.g., games published in the last N days) - **Static/genre categories** (tag-based): - Horror - Arcade - Platformer - Puzzle - (and other game genres) The system should support: - Listing games in a given category with pagination and basic sorting (e.g., by popularity, rating, release date). - Efficient updates of dynamic categories as new purchases and releases happen. #### 2. Game detail page For each game, users should be able to view a **rich media** detail page, including: - Text description, title, publisher information - Screenshots and/or video trailers - Price, platform compatibility, and other metadata (e.g., age rating, tags) Assume media assets (images/videos) are stored in some object storage or CDN; you need to design how they are referenced and served at scale. #### 3. Purchase and download Users must be able to: - Purchase games (assume real-money transactions) - After purchase, download the game binary or installation package Consider: - User accounts and purchase history - Ensuring that only users who have purchased a game can download it - Generating secure, time-limited download URLs - Handling high download traffic (e.g., via CDN or specialized download servers) You can assume payment processing is integrated via a third-party payment gateway, but you should describe how your system interacts with it and records orders. #### 4. Ratings and reviews Users can: - Leave ratings (e.g., 1–5 stars) and text reviews for games they have used - View existing ratings and reviews per game, with features like: - Average rating per game - List of reviews with pagination and sorting (e.g., most recent, most helpful) Consider how to: - Store and index reviews - Efficiently compute and update aggregate metrics (e.g., average rating, review count) #### 5. Non-functional requirements (assume a reasonably large but not planet-scale startup) - The system should be **scalable** to millions of users and hundreds of thousands of games. - Availability should be high; occasional stale data (e.g., slightly delayed popularity rankings) is acceptable. - Reads (browsing, viewing game details) are much more frequent than writes (publishing games, purchases, reviews). ### Tasks Design the system end-to-end. In your answer, cover at least: 1. **High-level architecture**: Main services/components and how they interact (e.g., User Service, Game Catalog Service, Purchase Service, Review Service, Recommendation/Ranking Service, Media/Asset Service). 2. **Data modeling and storage**: Core data models (users, games, categories, purchases, reviews) and what types of databases you would use for each (e.g., relational vs NoSQL vs search index). 3. **Category and ranking computation**: How you would implement dynamic categories like top-selling and new releases, including update frequency, batch vs real-time, and data pipelines. 4. **Purchase and download flow**: Sequence of events when a user buys and then downloads a game, including interaction with payment gateway and generation of secure download links. 5. **Ratings and reviews design**: APIs, data storage, and how to efficiently serve review lists and aggregate ratings. 6. **Scalability and performance**: Caching strategies, use of CDNs, partitioning/sharding strategies, and approaches to handle spikes in traffic (e.g., a hit new game release). 7. **Reliability and consistency**: Which parts need strong consistency (e.g., purchase records), where eventual consistency is acceptable (e.g., top-selling rankings), and how you would handle failures and retries. You do not need to provide detailed code; focus on system design, data flow, and trade-offs. State any additional assumptions you make.