\begin{filecontents}{l3keys2e-class.cls}
\LoadClass{article}
%% \RequirePackage{l3keys2e}
\ProvidesExplClass{l3keys2e-class}{0000/00/00}{0.0}{test}
\DeclareKeys {
option1 .code:n = {\wlog{You~gave~`#1'~for~option1}}
}
\ProcessKeyOptions
\end{filecontents}
% Load the class with some options.
% The class itself recognises `option1', leaving `option2' and
% `option3' as global optons which are not yet used.
\documentclass[option1=check,option2=more stuff,option3=unused]
{l3keys2e-class}