How Load Balancers Distribute Millions of Requests Across Backend Servers

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As web applications scale from hundreds to millions of requests, a single server can quickly become overwhelmed and crash. Load balancers solve this by sitting between clients and multiple backend servers, routing each incoming request to an available machine. This approach, known as horizontal scaling, contrasts with vertical scaling, where a single server is upgraded with more CPU and RAM but still faces physical and cost limits. With load balancing, traffic is spread across several servers, so if one fails, the others continue handling requests without downtime. Key concepts in load balancing include routing algorithms, health checks, sticky sessions, and the distinction between Layer 4 and Layer 7 load balancing strategies.

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