Combine Short-URL-Service with Existing CMS on Nginx

Question

A while ago, I created a simple internal short URL service (with Django).
If an entry exists, for example, /abc (or whatever), it redirects to the stored, longer URL with a HTTP-Status of 301. So far, so good...

However, now I have the requirement to set up this service for the main website.

However, there is already a CMS running with nginx try_files and proxy_pass configured.

Nginx:

location / {
    try_files /maintenance.html $uri @cms;
}

location @cms {
    rewrite ^/(.*)/$     /$1    permanent;
    rewrite              ^(.*)$ /VirtualHostBase/$scheme/$host:$server_port/cms/VirtualHostRoot$1 break;
    proxy_pass           http://example_cms;

    include              /etc/nginx/cfg/proxy.conf;
    include              /etc/nginx/cfg/security.conf;
    gzip_static          on; # to serve pre-gzipped version
}

Can these be combined? So, the desired flow is as follows:

• if /abc found and returned in the short URL service, redirect with a HTTP Status from URL-Service;
• otherwise, use the CMS and display a URL from the CMS using try_files + rewrite + proxy_pass.
• If none of these apply, show a 404, which can also be served by the CMS.