I know the limit for the number of simultaneous presence subscriptions is there for a reason, it would give a too high performance hit if 10000 people each persistently subscribed to all the other 9999. But here we want just *one*, our application, to subscribe to everyone.

It seems Lync Server has simplified matters with Application Endpoints compared to OCS, being a "Trusted Application" opens the doors. I know an application can have multiple endpoints, but I wonder if this can be used in the way I think:

• If there are more people than and endpoint can subscribe to, can the same Trusted Application create more endpoints and go around that limit? (One endpoint would subscribe to "State" presence for eg. 1000 users, then a new endpoint would be created and subscribe to the next 1000 users...) I suppose in my program I could then have all events concerning one application endpoint routed to a handler/helper object, one instansiated for each appendpoint - but I'm not sure I'm reasoning correctly there...?
• Or would the limit on presence subscriptions be on the application and not on each endpoint?
• Are the limits in Lync Server the same as in OCS 2007 R2? What are the Lync Server limits?

Yep, that's one of our recommendations in our documentation: http://msdn.microsoft.com/en-us/library/gg437468.aspx

(snippet from our documentation)

There are several ways to deal with the problem of a large number of persistent subscriptions, resulting in an error response from Lync Server 2010.

• Because the limit is for each endpoint, the application can create multiple watcher endpoints to distribute the load.

• Because the limit is for each Lync Server 2010 pool, the administrator can distribute users across multiple pools to distribute the load.

• As a best practice for dealing with a large number of subscriptions, it is recommended that a UCMA 3.0 application limit the number of categories it subscribes to. This can be accomplished by supplying a filter when the endpoint is created. By limiting the number of categories, more subscriptions are allowed.