I have written many services resources on the DRUPAL, "n" number of API hit comes to the DRUPAL CMS and access the data in the DRUPAL database.
My question is, when I hit service, Is DRUPAL CMS calling the bootstrap and verify every modules is loaded or not ?
Because I am wondering, there are nearly 100 web services, no more DRUPAL UI is consumed in this project.
So web service will eat site performance ?
Each request to one of your services will bootstrap Drupal in order to be able to reliably uses its APIs. And yes, this is a performances hit since bootstrapping Drupal is not lightweight.
In addition, depending on how the services are build, they may not provide any kind of caching, unlike traditional pages. Also a Web Services driven page will probably require more than one request, increasing the load on the server.
So yes, Web Services may eat your site performances.