If you use multiple indexer sites to download nzb files an open source program called nzbhydra2, that can be found on github, might be handy. This tool is a meta search engine tool written in python and can be installed on your local machine or a dedicated server/vps/seedbox you are using for downloads.

You can simulatiously access the api search results from multiple indexers you have api access to. The tool also give some nice stats and offers an api itself.

You can also use it as a source for tools like Sonarr or CouchPotato.