Lesson 4 / 32

Load Balancing

Spreading traffic across servers for scale and failover.

Why load balance

A load balancer sits in front of a pool of identical servers, routing each request to a healthy one. It enables horizontal scaling and hides individual failures.

Algorithms

Round robin (simple), least connections (uneven request cost), consistent hashing (sticky routing to the same node — useful for caches).

L4 vs L7

L4 balances by IP/port (fast, dumb). L7 reads HTTP — can route by path, host, or cookie, do TLS termination and retries.

Avoid a single point of failure

The load balancer itself must be redundant — run a pair with a floating IP or DNS failover so it can't take down the whole system.