6 System Design Interview Concepts
This comprehensive guide will walk you through the essential concepts to master in order to excel in your system design interviews.
Introduction
Are you preparing for a system design interview, particularly for a senior engineering role? You’re in the right place. Unlike coding interviews, system design interviews are less about writing actual code and more about showcasing how you can construct an entire system. This comprehensive guide will walk you through the essential concepts to master in order to excel in your system design interviews.
Vertical and Horizontal Scaling
1. Vertical Scaling
The most straightforward way to scale your system is through Vertical Scaling. This involves upgrading your existing server by adding more RAM or a faster CPU.
Vertical scaling is often a quick fix for handling increased user loads. However, it’s not the most efficient way to scale in the long term.
2. Horizontal Scaling
A more efficient approach is Horizontal Scaling. In this scenario, replicas of the server are added so that each one handles a subset of requests.
This is a more robust solution compared to vertical scaling and it adds two key benefits:
Endless Scalability: You can keep adding servers.
Reliability: If one server fails, others can continue to fulfill requests, mitigating the single point of failure issue.
3. Load Balancing
To prevent server overload and to distribute traffic effectively, load balancing is essential.
A load balancer distributes incoming user requests across multiple servers, preventing any single server from becoming a bottleneck.
Algorithms
Load balancers use various algorithms to distribute traffic:
Least Connection: Sends traffic to the server with the fewest open connections.
Resource-Based: Chooses servers based on available resources.
IP Hash: Assigns traffic to servers based on a hash of the source and destination IP addresses.
Round Robin: Distributes traffic sequentially over a list of servers.
Custom Scripts: You can also write custom algorithms tailored to your needs.
Techniques
Popular methods for load balancing include:
Specialized Software: You can employ software like Nginx or use services like AWS Elastic Load Balancing for this purpose.
DNS-Based: Using DNS itself as a rudimentary load balancer by assigning multiple IPs for your domain. However, this approach offers less customizability.
4. Caching
Often the bottleneck in a system isn’t the web server but the database server. Caching involves temporarily storing data, often in a computer’s RAM, to serve future requests faster while reducing the load on the database.
Technologies
To implement caching, you’ll need to select from a range of available software options, such as Redis, Nginx, Memcached or Cassandra, based on your specific requirements.
Caching Invalidation
To keep the cache and database in sync, various cache invalidation strategies can be used. Choosing the right algorithm ensures that your cache remains both effective and efficient. Common algorithms are:
Write-through Cache: Update the cache and then the database.
Write-back Cache: Update the cache first, and synchronize with the database later.
But where is the Cache?
Caches can exist at different levels in your application architecture, including:
Client-Side: In the browser’s cache.
Server-Side: Using software like Redis or Memcached.
Database: Through query caching in databases like MySQL.
5. Content Delivery Networks (CDNs)
Another layer of caching is through Content Delivery Networks. CDNs are networks of servers spread across multiple locations to store and serve web content like images and videos. They store cached copies of your content across multiple geographical locations.
Setup
CDNs usually are set up in one of these ways:
Pull-based: The CDN fetches data from the origin server upon the first user request and caches it.
Push-based: The origin server pushes data to the CDN beforehand.
Well-known CDN providers include Cloudflare, Google Cloud CDN, Amazon CloudFront, and Microsoft Azure CDN.
6. API Design
API design serves as the contract between the client and the server. Here are key considerations when designing an API:
Type of API: When designing an API, first decide on the type: RESTful, GraphQL, or gRPC.
Communication Protocol: HTTP, WebSockets, etc.
Data Transport Mechanism: JSON, XML, or Protocol Buffers.
Security: Consider implementing measures against Dictionary Attacks, XSS, CSRF, HPP Attacks, and use Rate Limiting.
Querying and Sorting: How will the data be retrieved and sorted?
Pagination: You don’t wanna get all data in one request, you need to paginate.
Performance: Optimize the initial loading time of your app.
Error Handling: Make sure errors are consistent and informative.
Server-driven and Client-driven design
Depending on your application, you might opt for a server-driven or client-driven API design, each offering its own set of benefits.
Server-Driven: Useful for mobile apps where releases require app store approval.
Client-Driven: Offers more flexibility on the client side.
Conclusion
From scaling strategies and load balancing techniques to the nuances of caching and API design, mastering these areas can give you a strong edge over the competition.
If there are other topics or complexities you’d like us to learn, please leave a comment below.
For those who are also gearing up for coding interviews, be sure to explore this in-depth guide on how to solve interview coding problems.