MySQL / MariaDB change feeds
MySQL and MariaDB do not have any way for a TRIGGER to invoke anything outside of the MySQL/MariaDB server.  (To do so would be to create a security problem.)

Well, you could write a UDF that could do anything, and compile a special version of the server, etc.

You are probably better off polling, as you mentioned.  If there are thousands of updates per minute, the polling could "optimize" the fetch via GROUP BY and other techniques.