node.js safety of asynchronous array

var docs = [];

server.on('add', function(item){
    docs.push(item);
});

setInterval(function(){
    save(docs);
}, 3000);

var save = function(array) {
    var items = array.slice(0); // copy array
    array.length = 0; // clear array

    mongodb.insert(items, function(){
        // ...
    });
};

I would like to save documents to RAM and next save to mongodb. Is this code safe?

Mongodb server is in EU, application server is in US. It is added 2-3k items per sec to the base. I would like to decrease quantity of connections. My question: It is possible that during save to the base the variable will be modificate (in 'add')