Note the following about this graphic:

  • The User Code Service (SPUCHostService.exe) creates the sandbox worker processes and assigns each HTTP request to a sandboxed solution to one of these processes.
  • A sandbox worker process (SPUCWorkerProcess.exe) is the process in which custom code that is a part of a sandboxed solution executes.
  • A full trust proxy process (SPUCWorkerProcessProxy.exe) hosts the portion of the SharePoint object model that sandboxed solutions can access and enables second stage calls to the rest of the object model.

For more information, see Sandboxed Solutions Architecture, Sandboxed Solutions​, Sandboxed Solutions Execution Model, and Chapter 4: Sandboxed Solutions.

Dual Worker Process Model for SharePoint 2010 Sandboxed Solutions