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If they won't warn us, could you please warn us? - Fellow ALB user.
Sure. Whenever a "config change" (Note: this includes adding or removing targets to a target group, EG Autoscaling) happens on an ALB, the ALB drops all active connections, and re-establishes them at once, at high load, this obviously causes significant load spikes on any underlying service. You can see this happening by looking at the "Active Connection Count" graphs from your ALB, and adding or removing an instance…
i'm starting to realize real world testing is difficult on aws bc "on-demand" means we can push maximums