What is system design with an example?

System design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specific requirements. It involves understanding the problem that needs to be solved and designing a high-level solution that can efficiently handle different use cases, scalability, reliability, and maintainability.

Example of System Design: Designing a URL Shortener (like Bit.ly)

Let’s say you are tasked with designing a URL shortening service like Bit.ly. The goal is to create a service where users can input a long URL, and the system returns a shortened version. When users access the shortened URL, it redirects them to the original URL.

1. Requirements

• Functional requirements:
  • Convert long URLs into shorter ones.
  • Redirect users from the shortened URL to the original URL.
• Non-functional requirements:
  • The system should handle a high volume of read requests (redirections).
  • URLs should expire after a configurable period.
  • The system should be highly available and scalable.
• Constraints:
  • URL length should be as short as possible.
  • The system should support millions of URLs.

2. High-Level Design

To handle millions of users and URLs, the system needs to be designed with scalability and reliability in mind. Here's a high-level breakdown of how the system might be structured:

• API Layer: Users will interact with the system through an API, where they can submit long URLs and receive shortened URLs.
• Database: Store mappings between the short URLs and long URLs.
• Hashing/Encoding: When a long URL is submitted, it will be hashed or encoded into a unique shortened form. This can be done using techniques like Base62 encoding to keep the URL short.
• Redirection Service: When a user clicks on the shortened URL, the service will look up the original URL in the database and redirect the user.
• Cache: Since redirection requests will be frequent, a caching layer (like Redis) can be used to store the most commonly requested URLs to reduce database load.
• Load Balancer: A load balancer can distribute incoming traffic across multiple servers to ensure that the system scales horizontally.
• Monitoring and Analytics: Track how many times a short URL has been used and monitor the system for performance bottlenecks.

3. Components of the System

• Database: A NoSQL database like Cassandra could be used for high availability and scalability to store URL mappings.
• Hash Generation Service: To generate unique short URLs, we can use a hash function, or a distributed ID generator like UUID or a counter.
• Cache: Use Redis or Memcached to store frequently accessed mappings and reduce load on the database.
• CDN (Content Delivery Network): To improve performance and availability for global users, we can cache frequently requested URLs in a CDN.
• Redirection Logic: This service will handle redirecting the user from the short URL to the long URL efficiently.

4. Challenges in the Design

• Scalability: As the number of users and URLs grows, the system should be able to scale horizontally.
• Hash Collisions: Ensure that the hash generation method doesn’t create duplicates for different URLs.
• URL Expiry: Implement logic to handle expiration of URLs (e.g., after 1 year) and ensure proper cleanup.
• Data Consistency: Ensure consistency between database and cache layers, especially during updates.

5. Outcome

The designed system allows users to shorten long URLs and ensures that the shortened URLs can handle a large number of redirection requests with low latency. By leveraging caching, load balancing, and a distributed database, the system is scalable and highly available.

Learn More with System Design Courses

To dive deeper into system design concepts and become proficient in designing scalable and robust systems, consider taking the Grokking System Design Fundamentals by DesignGurus.io. This course is ideal for beginners and covers foundational system design concepts.

For more advanced system design interviews and scenarios, you can explore:

• Grokking the System Design Interview: Perfect for preparing for system design interviews at tech companies.
• Grokking the Advanced System Design Interview: This course covers more complex design problems and advanced system design techniques.

Conclusion

System design involves creating the blueprint for a system that meets both functional and non-functional requirements while being scalable, reliable, and maintainable. By understanding user needs, identifying constraints, and architecting components like databases, caching, and load balancing, you can create efficient systems. DesignGurus.io offers a range of courses to help you master these concepts and succeed in system design interviews.