Dynamically loading terms in a term reference tree from a huge taxonomy so users may select nodes as options I'm trying to create a form that uses a bushy taxonomy of about 30,000 (max depth is ~9) terms to allow users to select multiple nodes from the tree.  The Taxonomy Term Reference Tree Widget fits the functionality I need perfectly, but with the size tree that I'm using each expand/collapse or select event takes a couple of seconds to complete, which isn't acceptable in terms of performance.

I'm new to drupal, but haven't been able to find a widget that can perform this task quickly. Are there any D7 widgets or modules that can accomplish this task? It seems that if I were able to have the widget not load all of the children all at once that performance might increase, but I can't say I'm sure.
You can try some contrib modules:
Hierarchical Select  


  Module defines the "hierarchical_select" form element, which is a
  greatly enhanced way for letting the user select items in a hierarchy. Demo


Simple hierarchical select  


  Defines a new form widget for taxonomy fields to select a term by
  "browsing" through the vocabularies hierarchy.


You can use it with High-performance JavaScript callback handler 

Also you can try https://www.drupal.org/project/views_jstree