We have around 20K vm's managed in our vRA instance and I use this to retrieve a vCAC:VirtualMachine by name:
var vCACVms = Server.findAllForType("vCAC:VirtualMachine", "VirtualMachineName eq '" + vCACVmName + "'");
Gives me an array of any matches.
To find the catalog resource by name I use:
Both of these return near immediate results.
Thanks, that helps.