What is System Design?

System design is the process of taking a set of requirements and building a product that fulfills those requirements.

Let’s Design a System

Let’s consider the example of building Facebook to understand system design better.

Architecture

• To design a system like Facebook, the first step is deciding on the architecture.
• Key architectural components include:
  • Database: To store user data.
  • API Server: To serve requests from users and other systems.
  • CDNs (Content Delivery Networks): To efficiently serve assets like images.
• The high-level architecture defines which all component are required, how these components interact and fit together.

Components

• Once the architecture is in place, the next step is identifying the major components needed to power the system.
• For example, in Facebook:
  • One component handles Authentication and Authorization.
  • Within this component, we might need:
    • 1 App Server to process authentication logic.
    • 1 Database to store user credentials securely.
    • 1 Cache to speed up repeated queries.

Modules

• After deciding on the components, the final step is breaking them into modules.
• For each component, determine what modules are required to implement it effectively.
• For example:
  • The Authentication and Authorization component can have modules like:
    • User registration.
    • Login and session management.
    • Token validation.

Bringing It All Together

• System design involves three strong pillars:
  1. Architecture: The overall blueprint of the system.
  2. Components: The building blocks of the system.
  3. Modules: The smaller pieces within components that handle specific tasks.
• More importantly, system design ensures that all these different parts come together and interact seamlessly to solve the bigger problem—in this case, building Facebook.

The Product Development Lifecycle

In organizations, product development typically follows this structure:

1. Architecture → 2. Components → 3. Modules

Every single tech product is a “system” that has been “designed.”

When We Design a System

When designing a system, we:

1. Break down the problem statement into solvable sub-problems.
2. Decide on the key components and their responsibilities.
3. Define the boundaries (scope) of each component.
4. Address key challenges in scaling the system.
5. Make the architecture fault-tolerant and reliable (available).

By following these steps, we can design systems that are scalable, robust, and effective in solving real-world problems.