Lesson 4 / 32
Load Balancing
Spread traffic across servers with load balancers, compare L4 and L7 and routing algorithms, and avoid a single point of failure.
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.