Loading...
The system must provide essential functionalities for users to create, view, edit, and delete advertisements. Each advertisement should include fields such as a title, description, price, and category. Additionally, users should be able to browse through advertisements based on categories and perform searches based on keywords.
To enhance user experience and provide scalability, the system should also allow user authentication and authorization. A rating system for advertisements could improve trustworthiness, and an internal messaging system might facilitate communication between buyers and sellers. Required non-functional requirements include high availability, low latency, and the ability to handle millions of concurrent users.
To estimate the resources needed for a system like Craigslist, we can start by evaluating potential traffic. Assuming 1 million daily active users posting, viewing, and managing ads, and estimating that each user generates an average of 10 requests per session translates to about 10 million requests daily. This results in approximately 115 transactions per second (TPS). Based on industry benchmarks, a simple service can handle about 100 TPS on a single instance. Thus, we'll likely need at least 2-3 web service instances behind a load balancer.
For the database, we can estimate users and ads. If each active user has about 5 ads, we need to manage around 5 million records in a NoSQL database. Given this size, a sharded database architecture can help distribute load. We must also consider storage for user profiles and potential images for the ads. A storage estimate stands at around 1GB per 1000 ads, suggesting we may need around 5TB for our photo storage, using cloud-based storage solutions.
The following RESTful API endpoints are proposed:
Furthermore, we might implement rate limiting on these endpoints (e.g., 10 requests per minute) to prevent abuse. Furthermore, authentication should leverage OAuth 2.0 to ensure user data security, coupled with JWT tokens for session management.
The system will employ a NoSQL database, such as MongoDB, for flexible schema management to accommodate the varying advertisement types. Each advertisement document could have fields like title, description, price, category, location, and userID. We'll also store user data in a separate collection including fields like username, email, and password_hash.
A relational database could also complement the system for managing user profiles, ratings, and transaction history. The relationships will be users to ads (one-to-many) and users to ratings (one-to-many), providing a clear mapping of interactions between entities.
The high-level architecture includes a client application (web/mobile), a load balancer, and several microservices functioning behind the scenes:
The request flow diagram illustrates how a typical user request would process through the system:
The major components in this system design include:
The major trade-offs in designing a system like Craigslist include:
Addressing potential failures is crucial for maintaining system reliability:
Once the core functionalities are established, future enhancements could include: