Totally depends on how “disciplined” the team’s DevOps practices are. In theory it should be as easy as updating a config parameter as you say, but my experience tells me that it’s sometimes not the case.
Especially with these kind of fundamental, core services such as Consul provides, it’s not unheard of to have templates with static machine allocations (as opposed to everything in a single auto-scaling group). It’s a bit of a shortcut, but it’s often a bit hairy to implement these services using true auto-scaling.
Having said all this, doing these types of migrations when things are already completely broken / on fire makes things a lot easier: you don’t care about downtime. So then it can be as simple as restarting all instances using a new instance type, downtime be damned.
Especially with these kind of fundamental, core services such as Consul provides, it’s not unheard of to have templates with static machine allocations (as opposed to everything in a single auto-scaling group). It’s a bit of a shortcut, but it’s often a bit hairy to implement these services using true auto-scaling.
Having said all this, doing these types of migrations when things are already completely broken / on fire makes things a lot easier: you don’t care about downtime. So then it can be as simple as restarting all instances using a new instance type, downtime be damned.