Load Balancer
Task: Keep serving requests when a server dies
What you are watching
How a load balancer works. Clients send requests to a single balancer, which forwards each one to the next server in turn, round robin, so the load spreads evenly across three servers. When the third server stops answering its health check, the balancer removes it from the pool and reroutes subsequent requests to the two that remain. No request is dropped and the client never sees the failure.