Skype for Business and Lync 2013 clients manage memory differently than previous client versions. This article describes the design change, how it impacts client performance, and how it affects the memory footprint. For purposes of this article, the term “Lync 2013” relates to Lync 2013 and Skype Business clients. At the time of this writing, the executable name for Lync 2010, 2013 and Skype for Business clients is lync.exe.
Read more at source: https://blogs.technet.microsoft.com/nexthop/2016/01/14/skype-for-business-and-lync-2013-memory-usage/