[development] Alternative to drupal_bootstrap when we want to access Drupal data from other application?

Hello, I want to use some Drupal7 functions such as node_load, taxonomy_term_load in my custom written PHP applications. I managed to use them by running a full drupal bootstrap, function is okay, i.e. drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL); $node = node_load(123); However, when profiling the code using Xdebug, I found drupal_bootstrap is just too heavy, i.e. used 80% of my application CPU time even I am doing simple query such as node_load. Of course, I can direct query the Drupal DB but I don't want to reinvent the wheel, but now seems it is too much overhead. Any suggestion when outside application want to access Drupal data, for the above basic query (read only)? Thanks.