Understanding System Design: The 30 Key Concepts for Beginners

System design is often seen as a daunting topic, but it doesn't have to be! Once you break it down into core concepts, it becomes much easier to understand and implement. In this blog post, we’ll explore 30 essential system design concepts and explain them with simple, real-world examples. 1. Client-Server Architecture Client-server architecture is the backbone of most modern web applications. In this setup, the client (like a browser or mobile app) makes requests to the server (a powerful machine) that processes these requests and sends back data. Example: When you visit a website, your web browser (client) sends a request to a server, which processes it and returns the webpage content to your browser. 2. IP Addresses An IP address is like a phone number for a server. It uniquely identifies a device on a network. Every server on the internet has a unique IP address, and this is how the client knows where to send requests. Example: When you type facebook.com in your browser, your browser connects to Facebook’s server by using the server’s unique IP address, like 69.63.176.13. 3. Domain Name System (DNS) The DNS (Domain Name System) is like a phone book for the internet. It maps human-readable domain names (like google.com) to IP addresses (like 172.217.5.68) that computers use to identify each other. Example: Instead of typing the IP address of a website, you type google.com in the browser. DNS converts it into the IP address that helps you connect to Google’s server. 4. Proxy / Reverse Proxy A proxy is an intermediary between the client and the server. It forwards requests from clients to the server and can improve security. A reverse proxy works the opposite way and forwards client requests to a backend server. Example: A company may use a proxy server to filter and monitor employees' internet traffic, while a reverse proxy may distribute incoming web traffic across multiple backend servers in a large system. 5. Latency Latency is the delay between sending a request and receiving a response, often caused by the physical distance between the client and the server. Low latency is important for performance, especially in real-time applications. Example: If you're accessing a website hosted in New York while you’re in India, the data has to travel a long distance, causing a delay (latency) in loading the page. 6. HTTP / HTTPS HTTP (HyperText Transfer Protocol) is the protocol used by browsers to communicate with servers. HTTPS is the secure version of HTTP, encrypting the communication to ensure data privacy. Example: When you log into your online bank account, your browser uses HTTPS to encrypt your login details so they can’t be intercepted by hackers. 7. APIs (Application Programming Interfaces) An API is like a bridge between the client and the server. It allows your app to communicate with the server and get back the data it needs, without worrying about how things work on the backend. Example: When you use an app like Uber, the app communicates with the server via APIs to request data like available cars, prices, etc., and the server sends the data back. 8. REST (Representational State Transfer) REST is a set of rules for building APIs. It uses HTTP methods like GET, POST, PUT, and DELETE to interact with resources (data objects like users, orders, etc.) on the server. Example: When you submit a form on a website, a POST request is sent to the server to store your data. Similarly, a GET request retrieves data like your profile information. 9. GraphQL GraphQL is a more flexible alternative to REST. It allows clients to specify exactly what data they need, rather than getting a fixed response from the server. Example: In a REST API, to get both a user’s profile and recent posts, you may need to make two requests. With GraphQL, you can get all the data in one request by specifying what you need in the query. 10. Database A database is a place where your app stores and retrieves data. It helps organize and structure your data so it’s easy to access and manage. Example: A social media app like Instagram stores users’ posts, comments, and likes in a database so it can quickly fetch the data whenever needed. 11. SQL vs NoSQL SQL databases store data in tables with a predefined schema and are great for relational data. NoSQL databases, on the other hand, store unstructured or semi-structured data and are more scalable. Example: A banking application might use an SQL database to store transaction data, while a social media platform might use NoSQL for flexible storage of user-generated content like posts, images, etc. 12. Vertical Scaling Vertical scaling means adding more resources (like RAM, CPU) to a single server to handle more load. Example: If a server hosting a website experiences slowdowns during high traffic, upgra

Apr 19, 2025 - 16:09

Understanding System Design: The 30 Key Concepts for Beginners

System design is often seen as a daunting topic, but it doesn't have to be! Once you break it down into core concepts, it becomes much easier to understand and implement. In this blog post, we’ll explore 30 essential system design concepts and explain them with simple, real-world examples.

1. Client-Server Architecture

Client-server architecture is the backbone of most modern web applications. In this setup, the client (like a browser or mobile app) makes requests to the server (a powerful machine) that processes these requests and sends back data.

Example: When you visit a website, your web browser (client) sends a request to a server, which processes it and returns the webpage content to your browser.

2. IP Addresses

An IP address is like a phone number for a server. It uniquely identifies a device on a network. Every server on the internet has a unique IP address, and this is how the client knows where to send requests.

Example: When you type facebook.com in your browser, your browser connects to Facebook’s server by using the server’s unique IP address, like 69.63.176.13.

3. Domain Name System (DNS)

The DNS (Domain Name System) is like a phone book for the internet. It maps human-readable domain names (like google.com) to IP addresses (like 172.217.5.68) that computers use to identify each other.

Example: Instead of typing the IP address of a website, you type google.com in the browser. DNS converts it into the IP address that helps you connect to Google’s server.

4. Proxy / Reverse Proxy

A proxy is an intermediary between the client and the server. It forwards requests from clients to the server and can improve security. A reverse proxy works the opposite way and forwards client requests to a backend server.

Example: A company may use a proxy server to filter and monitor employees' internet traffic, while a reverse proxy may distribute incoming web traffic across multiple backend servers in a large system.

5. Latency

Latency is the delay between sending a request and receiving a response, often caused by the physical distance between the client and the server. Low latency is important for performance, especially in real-time applications.

Example: If you're accessing a website hosted in New York while you’re in India, the data has to travel a long distance, causing a delay (latency) in loading the page.

6. HTTP / HTTPS

HTTP (HyperText Transfer Protocol) is the protocol used by browsers to communicate with servers. HTTPS is the secure version of HTTP, encrypting the communication to ensure data privacy.

Example: When you log into your online bank account, your browser uses HTTPS to encrypt your login details so they can’t be intercepted by hackers.

7. APIs (Application Programming Interfaces)

An API is like a bridge between the client and the server. It allows your app to communicate with the server and get back the data it needs, without worrying about how things work on the backend.

Example: When you use an app like Uber, the app communicates with the server via APIs to request data like available cars, prices, etc., and the server sends the data back.

8. REST (Representational State Transfer)

REST is a set of rules for building APIs. It uses HTTP methods like GET, POST, PUT, and DELETE to interact with resources (data objects like users, orders, etc.) on the server.

Example: When you submit a form on a website, a POST request is sent to the server to store your data. Similarly, a GET request retrieves data like your profile information.

9. GraphQL

GraphQL is a more flexible alternative to REST. It allows clients to specify exactly what data they need, rather than getting a fixed response from the server.

Example: In a REST API, to get both a user’s profile and recent posts, you may need to make two requests. With GraphQL, you can get all the data in one request by specifying what you need in the query.

10. Database

A database is a place where your app stores and retrieves data. It helps organize and structure your data so it’s easy to access and manage.

Example: A social media app like Instagram stores users’ posts, comments, and likes in a database so it can quickly fetch the data whenever needed.

11. SQL vs NoSQL

SQL databases store data in tables with a predefined schema and are great for relational data. NoSQL databases, on the other hand, store unstructured or semi-structured data and are more scalable.

Example: A banking application might use an SQL database to store transaction data, while a social media platform might use NoSQL for flexible storage of user-generated content like posts, images, etc.

12. Vertical Scaling

Vertical scaling means adding more resources (like RAM, CPU) to a single server to handle more load.

Example: If a server hosting a website experiences slowdowns during high traffic, upgrading the server with more CPU and RAM is an example of vertical scaling.

13. Horizontal Scaling

Horizontal scaling involves adding more servers to share the load. This approach allows systems to grow without relying on a single server’s capacity.

Example: If one server hosting an online store can't handle all the traffic, horizontal scaling would involve adding more servers and distributing the requests across them.

14. Load Balancer

A load balancer distributes traffic across multiple servers to prevent one server from becoming overwhelmed.

Example: If you have multiple web servers hosting a popular website, a load balancer will ensure the incoming traffic is split evenly, so no single server is overloaded.

15. Indexing

Indexing is a technique used in databases to speed up data retrieval. It’s like an index in a book, which helps you quickly find the content you’re looking for.

Example: If you have a large database of books, indexing the title column will allow you to quickly find a book by its title without scanning the entire table.

16. Replication

Replication involves creating copies of the database on different servers to improve read performance and fault tolerance.

Example: If your application has millions of users, you can have several read replicas of the database to spread out the traffic and improve read performance.

17. Sharding

Sharding involves splitting a large database into smaller pieces (called shards), each of which is stored on a separate server. It helps distribute the load across multiple machines.

Example: If you have millions of users, you can shard the database based on user IDs, so different shards handle different user data, making it easier to scale.

18. Vertical Partitioning

Vertical partitioning splits a database table into smaller parts based on columns. This optimizes performance for queries that require specific columns.

Example: If you have a table with user data (name, email, login history, and billing), but often only need the name and email, vertical partitioning allows you to separate them into two tables.

19. Caching

Caching stores frequently accessed data in memory to speed up retrieval and reduce database load.

Example: In an e-commerce app, if a user frequently checks a product’s price, caching the price in memory means it doesn’t have to be fetched from the database each time, speeding up the app.

20. Denormalization

Denormalization reduces the need for joins by combining related data into one table, which can speed up read operations but at the cost of more storage.

Example: Instead of having separate tables for users and orders, you combine them into one table that stores both the user’s data and their orders, improving read performance.

21. CAP Theorem

The CAP theorem states that in a distributed system, you can achieve only two of the following three: Consistency, Availability, and Partition Tolerance.

Example: In a chat app, you might prioritize Availability (ensuring users can always send messages) and Partition Tolerance (the system still works when parts of the network are down), but may sacrifice Consistency (some messages may be delayed).

22. Blob Storage

Blob storage is designed to store large files, such as images, videos, and documents. It's efficient for managing unstructured data.

Example: A video streaming service like YouTube uses blob storage to store and serve videos to users.

23. Content Delivery Network (CDN)

A CDN delivers content from servers that are geographically closer to the user, reducing latency and speeding up load times.

Example: When you stream a video on Netflix, the content is served from the nearest CDN server to you, reducing buffering time and improving the streaming experience.

24. WebSockets

WebSockets enable two-way communication between the client and the server over a single persistent connection. They are ideal for real-time applications.

Example: In an online multiplayer game, WebSockets allow the server to instantly update all players with the latest game data in real-time.

25. Web Hooks

Webhooks allow one server to notify another when a specific event occurs, without the need for polling.

Example: When you make a payment via Stripe, Stripe sends a webhook to your server to notify you that the transaction was successful.

26. Microservices

A microservices architecture breaks down an application into smaller, independent services, each responsible for a specific task.

Example: An online shopping platform might have separate microservices for handling payments, user accounts, and product inventory.

27. Message Queues

Message queues help manage communication between services asynchronously, which improves scalability and prevents overload.

Example: If a user uploads a video, instead of processing the video immediately, a message queue can place the request in line for later processing, ensuring the system isn't overwhelmed.

28. Rate Limiting

Rate limiting restricts the number of requests a user can make in a given time frame to protect the system from overload.

Example: If a bot tries to make hundreds of requests per second to your website, rate limiting will restrict it to a certain number of requests, ensuring normal users aren't affected.

29. API Gateway

An API Gateway is a single entry point that routes requests to different microservices and handles tasks like authentication, rate limiting, and logging.

Example: In a large application with multiple services, instead of contacting each service directly, the API Gateway acts as a mediator for all requests.

30. Idempotency

Idempotency ensures that repeated requests produce the same result. This is critical in operations like payments, where sending the same request multiple times shouldn’t result in duplicate actions.

Example: If you try to make a payment twice, idempotency ensures that the payment is processed only once, preventing duplicate charges.

Conclusion

These 30 system design concepts provide the foundation for building scalable and reliable systems. Whether you're designing databases, improving performance, or ensuring security, understanding these key concepts will help you navigate the complexities of system design.

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