A company is migrating a legacy application to AWS. The company manually installs and configures the legacy application on Amazon EC2 instances across multiple Availability Zones. The company sets up

The weighted random routing algorithm with automatic target weights (ATW) is incompatible with application-based sticky sessions on ALB. When session affinity (sticky sessions) is required, the target group should use a routing algorithm that properly supports it. The least outstanding requests algorithm is compatible with sticky sessions and ensures that requests from the same session are consistently routed to the same target, resolving the random application errors caused by sessions being split across different instances.

Anomaly mitigation is a feature used with weighted random routing to route traffic away from unhealthy targets, but it does not resolve the fundamental incompatibility between weighted random routing and sticky session requirements.

Disabling cross-zone load balancing would restrict traffic distribution to targets within the same Availability Zone but would not fix the session affinity issue caused by the weighted random routing algorithm distributing session requests to different targets.

Increasing the deregistration delay extends the time a deregistering target continues to receive existing connections, but this does not address the core issue of the weighted random algorithm not properly maintaining session affinity across active targets.