Why Learn System Design?

Applications serving 100 users differ fundamentally from those serving millions. Understanding principles is crucial for scalability and interviews.

Key Concepts

Scalability = Handling increased load
Availability = Running without downtime
Consistency = Data accuracy across system
Partition Tolerance = Operating despite failures

Horizontal vs Vertical Scaling

Vertical (Scale Up):
- Increase single server power
- Limited and expensive

Horizontal (Scale Out):
- Add more servers
- Flexible, requires different architecture

Load Balancing

Client → Load Balancer → Server 1
                       → Server 2
                       → Server 3

Algorithms:
- Round Robin
- Least Connections
- IP Hash

Caching Strategies

Client → CDN → Load Balancer → App → Cache → DB

Strategies:
- Cache-Aside: App manages cache
- Write-Through: Write to cache and DB
- Write-Behind: Write cache, async DB

Conclusion

System design experience comes from practice. Study real systems like Twitter, Netflix, and Uber architectures.