Serving API from another site behind the first one - apache

Question

I have old solution based on Drupal 7 and the new one based on Drupal 8. Both of them provide APIs for their mobile apps. (URLs can be easy distinguished) In order to maintain smooth migration for users I want to keep old solution working as it is and serve new version of API behind it, it has obvious difference in pattern like /oauth/token, /api/v1/, /api/v2/.
I have tried the different ways of configuring apache with I different results, but not exactly what I need. I tried:
Configuring virtual hosts together with Alias;
Changing DocumentRoot to /var/www (where I have docroot with and docroot-new)
Configuring the .htaccess different ways
<VirtualHost *:80>
ServerName ${APACHE_SERVERNAME}
ServerAlias test.*
DocumentRoot /var/www/docroot/
#this is example with phpinfo, works well
Alias "/info.php" "/var/www/docroot-new/"
#Just to simplify I'm trying to serve only one API endpoint from
new solution
Alias /api/v1/mobile-ui/ "/var/www/docroot-new/"
#And auth endpoint
Alias "/oauth/token/" "/var/www/docroot-new/"
</VirtualHost>
<Directory "/var/www/docroot/">
DirectoryIndex index.php
Options Indexes FollowSymLinks
AllowOverride All
Order allow,deny
Allow from all
Require all granted
</Directory>
<Directory "/var/www/docroot-new/">
DirectoryIndex index.php
Options Indexes FollowSymLinks
AllowOverride All
Order allow,deny
Allow from all
Require all granted
</Directory>
In this case the old solution is served well, but the new one can't be handled appropriately.
If I change DocumentRoot to /var/www/ , then both of them will work well, but obviously with a dir name in url. I guess .htaccess can help me here, but I'm not an expert and can't find the solution.
I also switch-on addition logging for apache and able to check details like matching for mod_rewrite (actually not very helpful for me)

Answer 1

so, I find the solution by myself. It's even better than previous thoughts. Just proxying queries.
ProxyPassMatch "/api(.*)" "http://new-solution.local/api$1"
ProxyPassReverse "/api(.*)" "http://new-solution.local/api$1"
ProxyPass "/oauth/token" "http://new-solution.local/oauth/token"
ProxyPassReverse "/oauth/token" "http://new-solution.local/oauth/token"
Hope it will help someone to solve similar problem.