System Design Interview Cheat Sheet for Full Stack Engineers

System design interviews check your ability to build scalable, resilient architectures. Here are the core building blocks.

1. Horizontal vs Vertical Scaling

• Vertical Scaling (Scaling Up): Adding more RAM and CPU to a single server. Limited by hardware capacity.
• Horizontal Scaling (Scaling Out): Adding more servers to a resource pool. Requires a load balancer.

2. Load Balancers

Distribute network traffic across multiple servers. Algorithms include:

• Round Robin: Sequential distribution.
• Least Connections: Sends traffic to the server with fewest active sessions.
• IP Hash: Distributes based on client IP addresses (good for sticky sessions).

3. Caching Strategies

Use caching to reduce database loads. Popular strategies:

• Cache-Aside: Application queries cache first, reads from DB on cache miss and updates cache.
• Write-Through: Application writes to cache and DB simultaneously.
• Write-Behind (Write-Back): Application writes to cache first, DB updated asynchronously later.

4. SQL vs NoSQL Databases

Final Thoughts

Always start by asking clarifying questions about scale, budget, and system constraints before drawing any boxes.

Happy Coding!