Events are not indexing after upgradtion 5.6 to 6.0

What I did was , followed this post Help please.. breaking changes? - #10 by Maekee
and
Changed the logstash output to this:
index => "%{[@metadata][beat]}-%{[@metadata][version]}-%{+YYYY.MM.dd}"

I was not using any index templates for mapping, still I dont understand why it started working!!!

Regards