Load Balancing Mastery

Load balancing is the art of distributing incoming network traffic across multiple servers. This ensures that no single server is overwhelmed and provides high availability. If one server dies, the load balancer simply shifts the traffic to the survivors.

1. Layer 4 vs Layer 7

• Layer 4 (Transport): Balances based on IP address and Port. It is extremely fast but doesn't understand the content (e.g., "This is a request for /images").
• Layer 7 (Application): Understands the HTTP request. It can route traffic based on the URL path, Cookies, or Headers. This is what we use for Microservices.

2. Nginx Ingress Controller

In Kubernetes, the **Ingress Controller** (often powered by Nginx) is the entry point for all web traffic. It handles SSL termination (HTTPS) and uses rules to route toolliyo.com/api/users to the Identity service and toolliyo.com/api/catalog to the Catalog service.

4. Interview Mastery

Q: "What is 'Sticky Sessions' (Session Affinity) and why should we avoid it in Microservices?"

Architect Answer: "Sticky Sessions ensure that a specific user always hits the same server instance. This is a hack used to support legacy stateful applications. In Microservices, we avoid it because it breaks **Scalability**. If one server gets stuck with 1,000 'Heavy' users, we can't easily move them to a quieter server. We prefer **Stateless Services** where ANY instance can handle ANY user, because the state is stored in a shared place like Redis."