Learn the difference between vertical scaling (bigger machines) and horizontal scaling (more machines). You should understand how Load Balancers (Nginx, HAProxy) distribute traffic using algorithms like Round Robin or Least Connections. 2. Databases & Storage
Store frequently accessed data in memory. Levels: client cache (browser), CDN (static assets), reverse proxy (dynamic content), database cache. Eviction policies: LRU, LFU, TTL. system design interview pdf download