Thank you, Christian!
I will adjust my configuration and try out your suggestions.
At the same time I will improve my logstash configuration a little. Are there any settings that allow me to keep state in Logstash in the event that the service is restarted, so I do not have to reindex data that already has been indexed?
Edit: if it is only sincedb_path, then I already got it 
Edit #2: I updated my Logstash config and removed document_id, doc_as_upsert => true and action => update, and that solved my problem. Thank you once again!
