nodejs have db connection pool import module
var pool = mysql.createPool({
connectionLimit : 10,
host : 'example.org',
user : 'bobby',
password : 'pass'
});
pool.getConnection(function(err, connection){
if(err){
return cb(err);
}
connection.changeUser({database : "firm1"});
connection.query("SELECT * from history", function(err, data){
connection.release();
cb(err, data);
});
});