Willem first encountered Erlang in 1993. At that moment he was testing a number of ASN.1 tools at the research department of KPN. The Erlang ASN.1 application was one of these tools. Unfortunately he did not recognize the greatness of Erlang at that moment.

In 2005 Willem was working as an IT Architect for T-Mobile Netherlands. From some T-Mobile UK colleagues he heard stories about a programmer who would make changes to their Erlang system during the meeting in which they were discussing the requirements. Even if these stories were exaggerated, it was clearly very different from the development cycles at T-Mobile Netherlands and Willem decided to take a closer look at Erlang. This resulted in the creation of Erlsom (an XML parser) and some other hobby projects.

After having worked for more than 15 years as IT Solution Designer and IT Architect at various telecom operators, Willem decided that he had seen enough Word documents, Powerpoints and Visio pictures. In 2015 he started as a freelance Erlang programmer. Since then he has done various projects, including more open source projects (sponsored, this time): Erlang implementations of the SOAP and GRPC protocols. Since August 2017 he has been working mainly for Deribit, an online trading platform for Bitcoin futures and options.