Use this tag for Apache version 2.4.x specific question.
Apache 2.4 has improved caching, proxy modules as well as new session control
Run-time Loadable MPMs
Event MPM
Better support for asynchronous read/write for supporting MPMs and platforms.
A new expression parser allows to specify complex conditions using a common syntax in directives like SetEnvIfExpr, RewriteCond, Header, , and others.