When working with WCF especially when middle-tier client applications uses Windows Communication Foundation, you sould always think about performance and take some major design decisions and tuning parameters. WCF client not generated as a proxy via SvcUtil.exe (Relevant more in .NET 3.0. In .NET 3.5 major performance improvement was made on WCF proxy creation). Client shares service contract and schema (model classes as data contract). Cache WCF proxy as a static member One instance, once instance...