#🧱 Building Block: Load Balancer

#Overview

A Load Balancer (LB) distributes incoming network traffic across a group of backend servers, also known as a server farm or server pool.

#Key Concepts

• L4 Load Balancing: Operates at the transport layer (TCP/UDP). Faster but lacks content awareness.
• L7 Load Balancing: Operates at the application layer (HTTP/HTTPS). Can route based on URL path, headers, or cookies.
• Health Checks: Periodically checking if backend servers are responsive before sending traffic.

#Algorithms

• Round Robin: Distributes requests sequentially.
• Least Connections: Sends requests to the server with the fewest active connections.
• IP Hash: Uses the client's IP address to determine which server receives the request (session persistence).
• Consistent Hashing: Minimizes disruption when servers are added or removed.

#When to Use

• Scalability: When a single server cannot handle the traffic.
• High Availability: To ensure service continues even if some servers fail.

#Trade-offs

• Pros: Increases capacity, improves reliability, enables zero-downtime deployments.
• Cons: Becomes a single point of failure (unless configured in high-availability mode), adds latency.