Imagine your web application becomes extremely popular and thousands of users start visiting at once. A single server would struggle to handle all the requests, leading to slow performance or even crashes. This is the problem that load balancing solves.
Engagement Message
What happens to your experience when a popular website is slow to load?
Elastic Load Balancing (ELB) automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances. It acts as a single point of contact for clients, but spreads the work across a fleet of servers.
Think of it like a traffic cop directing cars into multiple open lanes to prevent a traffic jam.
Engagement Message
How is a load balancer similar to a traffic cop at a busy intersection?
A key function of a load balancer is to perform health checks on the servers behind it. It continuously monitors the health of its registered targets and will only send traffic to the ones it knows are healthy.
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If a server fails a health check, what should the load balancer do with traffic?
By distributing traffic and performing health checks, load balancers enable you to build applications that are both scalable and fault-tolerant. You can scale by adding or removing servers in response to demand. You achieve fault tolerance because traffic is automatically rerouted away from failed servers.
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Which of these benefits, scalability or fault tolerance, is more important during a sudden traffic spike?
AWS offers different types of load balancers. The most common is the Application Load Balancer (ALB). It operates at the application layer and is best suited for load balancing HTTP and HTTPS traffic. It's intelligent enough to route requests based on the content of the request itself.
