Perfon.WebApi is an open source performance monitoring .Net framework for Web Api 2 applications without using windows performance counters. It has built-in UI dashboard and Rest API. Collected data is stored in-memory cache, and/or in LiteDB embedded database, and/or in any custom storage driver. See simple how-to example on https://github.com/magsoft2/Perfon.Net
Support of MySQL for perfomance counters data storing.