Using the Elasticsearch Input Plugin on Active Indices

Hi there, so I am in a situation in which I need to process data which is only made available to me in an elasticsearch index. I was thinking about using an elasticsearch input --(process data as desired in logstash)-->elasticsearch output (in a new index).

However how will this react on an active index?? My ideal situation would be to have a continuous flow of some kind where as soon as data is added to index1, it is read, processed, and saved in index2. Is there a way to accomplish this??

I assume you are talking about Logstash here?
That input only does a single read, it doesn't reconnect every N seconds and read newer data.

You may need to build something for this use case.