We did a one-off ticket to disable rolling indexes for flex, but seems like the scope of changes we need to do is bigger than that. At a glance it seems like FLEX tier is handled closer to serverless tier and not free / dedicated one, in particular it seems like FLEX tier clusters don't have deployment items associated with them that we expect for replica sets. We should investigate the full scope of changes needed in compass to account for FLEX tier and implement them, otherwise FLEX tier clusters are not available in compass-web at the moment