How many simultaneous sets can libcouchbase handle?

var async = require("async");
var couchBase = require("couchbase");
 
var config = {
  "host": "localhost",
  "port": 8091,
  "username": "Administrator",
  "password": "password",
  "bucket": "requests"
};
 
couchBase.connect(config, function(err, bucket) {
  if (err) {
    console.log("Unable to connect to Couchbase bucket [" + config.bucket + "]", err);
    process.exit(1);
  }
 
  console.log("Connected to Couchbase.");
 
  var ids = [];
  var jsonDocs = [];
  for (var i = 0; i < 400; i++) {
    ids.push(i + "");
    jsonDocs.push({id:i + ""});
  }
 
  console.log("Saving [" + jsonDocs.length + "] docs");
  async.map(jsonDocs, function(doc, callback) {
    bucket.set(doc.id, doc, {}, function(err) {
      callback(err);
    });
  }, function(err, results) {
    if (err) {
      console.log("Unable to save all entries", err);
      process.exit(1);
    }
 
    console.log("Saved all entries");
    process.exit(0);
  });
});