Earlier quoted context omitted.
I'm building a podcast discovery app and I find myself being de-facto pulled towards modularity. It's because my feed checker is in Elixir, my site is WordPress-based, and I communicate between them using the WP API, and I'm using Google Cloud SQL, and Elasticsearch on its own virtual machine... The thing is though, the Elixir feed checker has its own database table that tracks whether it's seen an episode in a feed.…
I think your problem might be not expanding wordpress. PHP will gladly do the above through wordpress plugins and cron jobs. I built something similar and ended up going that way. The system is still running to this day. Sure, its not hip but gets the job done with miniml fuss and makes money.
Once these are doing anything other than rotating log files, can the system really be considered monolithic?