In a static-only symbolic link app to a wordpress directory, how can I make nginx send expires headers to use browser caching?

Expires headers are not available from "Symbolic link to static-only app" applications. Instead, you should create a "Symbolic link to static/cgi/php54 app" application, and then use a .htaccess file containing the following directives:

# Use some aggressive client-side caching.
# Results in *significant* speed increases for page elements that are used
# repeatedly.  The elements are totally cached, and no requests are made, not
# even to check if the item has been modified.  This means that you need
# to use a new filename to push new content to clients -- you can't just edit
# the file on the server because the clients won't request the new version.
<IfModule mod_headers.c>
    Header unset ETag
    Header unset Last-Modified
    Header set Expires "Fri, 04 Nov 2021 21:59:49 GMT"
</IfModule>

Another way to do this would be:

• Create a new static-only application (not the symlink app), with "expires max" in the extra info field.
• Move all of your static assets from their present locations to the static-only app directory.
• Delete the original directories, and create symlinks (with the "ln -s" comman) pointing to your static-only app directory in their place.