System Design Fundamentals: Load Balancing, Database Sharding & CDN

Designing systems for high availability requires horizontal scalability, intelligent load balancing, and strategic database partitioning.

1. Horizontal vs Vertical Scaling

Vertical scaling (adding CPU/RAM) has physical and financial limits. Horizontal scaling (adding server nodes behind a Load Balancer) provides unlimited growth potential.

2. Database Sharding & Partitioning

When a single database node cannot handle write traffic, horizontal sharding distributes table data across distinct database instances based on a Shard Key (e.g. user_id).

3. Content Delivery Networks (CDN) & Caching

Offload static assets and edge computing to CDNs (Cloudflare/CloudFront) to reduce origin server load and provide ultra-low latency worldwide.

Combine CDN edge caching with dynamic API response compression for optimal web performance.