Aqui está a configuração que encontrei que atendeu aos meus requisitos.
De fato, o uso de mod_proxy é necessário, porque mod_pagespeed não tem a capacidade de realmente solicitar solicitações. Essa configuração do VirtualHost funciona para receber solicitações de www.example.com como proxy para o conteúdo servido por outro servidor em origin.example.com. Remova o comentário das linhas ModPagespeedEnableFilters
para ativar recursos específicos do PageSpeed. Você pode ver o administrador do PageSpeed em www.example.com/pagespeed_admin.
<VirtualHost 1.2.3.4:80>
ServerName example.com
ServerAlias www.example.com
CustomLog /home/example/logs/access_log combined
ErrorLog /home/example/logs/error_log
<IfModule mod_proxy.c>
ProxyPass /pagespeed_admin !
ProxyPass /logs/ !
ProxyPass / http://origin.example.com/
ProxyPassReverse / http://origin.example.com/
ProxyPassReverseCookieDomain origin.example.com www.example.com
ProxyPreserveHost on
</IfModule>
<IfModule pagespeed_module>
ModPagespeed On
ModPagespeedMapRewriteDomain www.example.com origin.example.com
ModPagespeedMapRewriteDomain example.com origin.example.com
#ModPagespeedEnableFilters add_head
#ModPagespeedEnableFilters combine_heads
#ModPagespeedEnableFilters inline_import_to_link
#ModPagespeedEnableFilters outline_css
#ModPagespeedEnableFilters outline_javascript
#ModPagespeedEnableFilters move_css_above_scripts
#ModPagespeedEnableFilters move_css_to_head
#ModPagespeedEnableFilters combine_css
#ModPagespeedEnableFilters rewrite_css
#ModPagespeedEnableFilters fallback_rewrite_css_urls
#ModPagespeedEnableFilters rewrite_style_attributes
#ModPagespeedEnableFilters rewrite_style_attributes_with_url
#ModPagespeedEnableFilters flatten_css_imports
#ModPagespeedEnableFilters prioritize_critical_css
#ModPagespeedEnableFilters make_google_analytics_async
#ModPagespeedEnableFilters rewrite_javascript
#ModPagespeedEnableFilters rewrite_javascript_external
#ModPagespeedEnableFilters rewrite_javascript_inline
#ModPagespeedEnableFilters include_js_source_maps
#ModPagespeedEnableFilters combine_javascript
#ModPagespeedEnableFilters canonicalize_javascript_libraries
#ModPagespeedEnableFilters inline_css
#ModPagespeedEnableFilters inline_google_font_css
#ModPagespeedEnableFilters inline_javascript
#ModPagespeedEnableFilters local_storage_cache
#ModPagespeedEnableFilters rewrite_images
#ModPagespeedEnableFilters convert_jpeg_to_progressive
#ModPagespeedEnableFilters convert_png_to_jpeg
#ModPagespeedEnableFilters convert_jpeg_to_webp
#ModPagespeedEnableFilters convert_to_webp_lossless
#ModPagespeedEnableFilters insert_image_dimensions
#ModPagespeedEnableFilters inline_images
#ModPagespeedEnableFilters recompress_images
#ModPagespeedEnableFilters recompress_jpeg
#ModPagespeedEnableFilters recompress_png
#ModPagespeedEnableFilters recompress_webp
#ModPagespeedEnableFilters convert_gif_to_png
#ModPagespeedEnableFilters strip_image_color_profile
#ModPagespeedEnableFilters strip_image_meta_data
#ModPagespeedEnableFilters resize_images
#ModPagespeedEnableFilters resize_rendered_image_dimensions
#ModPagespeedEnableFilters inline_preview_images
#ModPagespeedEnableFilters resize_mobile_images
#ModPagespeedEnableFilters remove_comments
#ModPagespeedEnableFilters collapse_whitespace
#ModPagespeedEnableFilters elide_attributes
#ModPagespeedEnableFilters extend_cache
#ModPagespeedEnableFilters extend_cache_css
#ModPagespeedEnableFilters extend_cache_images
#ModPagespeedEnableFilters extend_cache_scripts
#ModPagespeedEnableFilters extend_cache_pdfs
#ModPagespeedEnableFilters sprite_images
#ModPagespeedEnableFilters rewrite_domains
#ModPagespeedEnableFilters trim_urls
#ModPagespeedEnableFilters pedantic
#ModPagespeedEnableFilters remove_quotes
#ModPagespeedEnableFilters add_instrumentation
#ModPagespeedEnableFilters convert_meta_tags
#ModPagespeedEnableFilters defer_javascript
#ModPagespeedEnableFilters dedup_inlined_images
#ModPagespeedEnableFilters lazyload_images
#ModPagespeedEnableFilters insert_dns_prefetch
#ModPagespeedEnableFilters in_place_optimize_for_browser
</IfModule>
<Location /pagespeed_admin>
AuthName "PageSpeed Admin"
AuthType Basic
AuthUserFile /home/example/etc/htpasswd
Require valid-user
Satisfy any
Allow from 127.0.0.1
</Location>
</VirtualHost>