Application Scenarios

Heavy-Traffic Applications

For an application with heavy traffic, such as a large portal or mobile app store, ELB evenly distributes incoming traffic to multiple backend servers, balancing the load while ensuring steady performance.

Sticky sessions ensure that requests from one client are always forwarded to the same backend server, improving access efficiency.

Figure 1 Session stickiness

Applications with Predictable Peaks and Troughs in Traffic

For an application that have predictable peaks and troughs in traffic volumes, ELB works with AS to allow backend servers to be added or removed to keep up with changing demands, improving resource utilization. One example is flash sale, which usually lasts only a few days or even several hours and during which demand on your applications increases rapidly in a short period. By combining ELB with AS, you can always run desired number of backend servers that matches to the load of your application.

Figure 2 Flexible scalability

Zero SPOFs

ELB routinely performs health checks on backend servers to monitor their healthy state. If a backend server is detected unhealthy, ELB will not route requests to this server until it recovers.

This makes ELB a good choice for services that require high reliability, such as official websites and web services.

Figure 3 Eliminating SPOFs

Cross-AZ Load Balancing

ELB can distribute traffic across AZs. When an AZ becomes faulty, ELB distributes traffic to backend servers in other AZs.

Banking, policing, and large application systems can use ELB to ensure high availability.

Figure 4 Traffic distribution to servers in one or more AZs