Why do my MongoDB simultaneous $push updates fail?
As a workaround for this bug, I recommend using findAndModify and the checking the results to make sure your update happened.
dbCollection.findAndModify({ "uuid": someUuid, "revision.versionNumber": someVersionNumber},[], { "$set": { "meta.someId": someId }, "$push": { "meta.someMessages": someMessage } }, {safe: true, 'new' : true}, function(err, updated){ if(err){ //handle the error } if(updated.meta.someMessages doesn't contain your message) { //try it again or report it to the client } });