I just looked at couchdb-lounge because I'm very interested in partitioning and hadn't heard about it.

The wiki unfortunately left the important questions unanswered. Does lounge handle the rebalancing when new shards are added/removed? Do I have to take the cluster offline to add new nodes? What are the failure modes (e.g. a node failing and coming back)? How is a replacement node bootstrapped?

Since none of that is mentioned I have my doubts that lounge is handling it adequately. But I'd be glad to hear otherwise!