What is the recommended Provider?

The WebSync Cache Provider is the recommended provider due to its performance at large scale. WebSync also provides an SQL provider which works well for small user bases, but the disk I/O and frequent SQL queries needed to synchronize the servers become a problem once you exceed a certain threshold on message throughput. If you are using the SQL provider and have started running into performance problems then you should switch to using the Cache provider as soon as possible.

The WebSync Cache provider is so stable, and performs so well at large scale, that it has been powering our cloud service, WebSync Cloud, for years now.