3.3.1 Load Balancing
A load balancer sits in front of a pool of app instances and picks one for each request. Algorithms include round-robin, least connections, and consistent hashing.
Why it matters
One process cannot serve all users. Balancing lets you add machines and survive a single instance dying.
How it is used
Health checks remove bad instances from the pool. Sticky sessions are a last resort — prefer stateless apps and shared stores (Redis, DB) so any instance can handle any user.