Load Balancing
How a load balancer spreads traffic across servers, the L4 versus L7 choice, common algorithms, health checks and sticky sessions.
What it is
A load balancer (LB) sits in front of several servers and forwards each incoming request to one of them. Clients talk to one address; the LB picks the server.
It gives you:
- Capacity: many servers share the work.
- Availability: if one server dies, the LB stops sending traffic to it.
- Flexibility: add or remove servers without clients noticing.
Real tools: Nginx, HAProxy, Envoy, AWS Elastic Load Balancing (ALB and NLB), Google Cloud Load Balancing.
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