Well Logstash can output data into Kafka or ElasticSearch. So you could for example transform logs to json or do simple text processing in Logstash and put it to ElasticSearch for logsearching but you can also put it in Kafka and then have a stream parsing with all sorts of tools like Flink, Spark, etc. 
You could then have the possibility do so some realtime analysis on what the user do all over your stack. Too many &quot;Login Failed&quot; events and maybe you have an attacker trying to bruteforce a passsword and maybe you need to present him with a captcha screen.