Common scenarios

Distribute workloads

CLB instances route traffic to Elastic Compute Service (ECS) instances that act as backend servers based on listening rules. This allows you to avoid overloaded servers that may negatively affect user experience. The session persistence feature can be used to forward all requests from a client to the same backend ECS instance to improve access efficiency.

Scale your applications

CLB can be used as traffic ingress points for both web servers and application servers. This allows you to scale the service capability of your applications by adding or removing backend ECS instances in response to business requirements.

Eliminate single points of failure (SPOFs)

CLB instances act as the single point of contact for clients. You can add multiple ECS instances to a CLB instance. When an ECS instance malfunctions, CLB automatically isolates the ECS instance and distributes inbound requests to other healthy ECS instances. This ensures that your applications continue to run as expected.

Implement zone-disaster recovery (multi-zone disaster recovery)

To provide more stable and reliable CLB services, CLB supports cross-zone deployment in most regions. You can deploy a CLB instance across multiple zones within the same region to improve disaster tolerance and ensure the reliability of your applications. When the primary zone fails or has no healthy ECS instances, the CLB instance can automatically fail over services to the secondary zone within 30 seconds. When the primary zone recovers, the CLB instance automatically switches services back to the primary zone.

Implement cross-region disaster recovery

You can deploy CLB instances in different regions and add the ECS instances of different zones within each of these regions to the CLB instance in the same region. You can use DNS to resolve domain names to the service addresses of CLB instances in different regions. This way, global load balancing is achieved by using CLB. When a region becomes unavailable, you can temporarily stop DNS resolution in the region without affecting user access.