Hi,all, Based on my discontinuously near ten years experience using exist-db, I made a plan to using exist-db to management more than millions people's EHR, till now, it almost can work, here is what I have done: 1) split the large quantity of doc into small collection( not one collection for one people, but one doc for one people), target to speed query personal info and insert new record nodes. 2) with the kind developer 's help , we can using new range index to quick query big data based on some conditions. 3) using the backup policy to do backup. ... But, there are still some difficult to worry about: 1) exist-db often caused corrupt for a heavy load query, and this often cause db recover fail. and how to avoid heavy load query to affect other query? 2) when will use re-index? after corrupt? the re-index process is very time consumed. how to accelerate re-index? 3) how to control concurrently update db? often this cause the db stop responding to xquery, and as 1). everyday there will more than 1000000 files add to the db, so this is a difficult problem. 4) how to control backup copys ? the backup file will cost large disk space if all old copy exist. Thanks for advice