Mark has been an Apache Tomcat committer since November 2003. He initially worked on Tomcat in his free time but since August 2008 he has been employed by SpringSource (now part of Pivotal) to work on Apache Tomcat. He spends most of my time working on Tomcat but he also works on tc Server, Pivotal's Servlet & JSP container based on Apache Tomcat.

He is the release manager Apache Tomcat 8.5 and 9 where he tries to release a new version every month or so. He is currently focused on Tomcat 9 development which supports Servlet 4.0. He was a member of the JCP expert group for JSR 369.

Elsewhere at the ASF, He is a member of the ASF security and infrastructure teams and he is also on the Commons PMC where he focuses on Commons Pool and DBCP.

He is a member of the ASF and has served as a Director since 2016.