A new ALB target group is enabled for slow start. A team registers EC2 instances as targets but finds the targets do not enter slow start. What is the reason the targets never entered slow start?

For ALB slow start to function, the target group must contain at least one healthy target that has been registered before slow start is enabled. If all targets are registered after slow start is enabled, or if no targets are healthy when slow start is enabled, the feature will not activate. The round robin routing algorithm is a standard distribution method and does not prevent slow start. The instance types of targets within a target group do not need to be uniform. The 5-tuple criteria is used for connection tracking, not for slow start functionality.