Apache 2.4 is not supported officially by mod_xsendfile, but it seems the EnableSendfile on configuration option that ships with my Apache 2.4 installation accomplishes the same thing. Switching to SENDFILE_BACKEND = 'sendfile.backends.xsendfile' improves performance with this setting on regardless of whether or not mod_xsendfile is installed on the machine. I may have gotten lucky with my configuration, but I think EnableSendfile on should be investigated as the long-term replacement for mod_xsendfile for this package.