While looking at the statistics for CouchBase monitoring, like ep_queue_size, vb_num_eject_replicas, ep_warmup_value_count, and vb_active_curr_items, I see that most of them are prefixed with ep_ or vb_. I have not been able to find any explanation on what these prefixes mean.
I have tried searching the docs at https://docs.couchbase.com/server/current/manage/monitor/monitoring-cli.html but have found nothing. I think it might be that ep_ stands for ephemeral bucket and vb_ stands for vBucket, but that's just a wild guess.