I am looking into this for a client at the moment but I don’t have much experience in this field. They are looking for the Wix Site to add and retrieve data from Mongo DB.
Hello,
here just found some posts, try to use the searchbar 
https://www.wix.com/corvid/forum/community-discussion/mongo-db-buffer-is-deprecated-bug
https://www.wix.com/corvid/forum/community-discussion/poor-man-s-transaction-tracking
https://www.wix.com/corvid/forum/community-discussion/error-importing-braintree-npm
https://www.wix.com/corvid/forum/community-discussion/need-some-info-for-presentation