when we can’t find a particular static file in its “usual” location, use its alternate.
RewriteEngine On
RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI} !-f
RewriteCond %{REQUEST_URI} ^/foo/bar/baz(.*\.png)$
RewriteRule ^/foo/bar/baz/(.*)$ /nfs/foo/bar/baz/$1