Is Elastic search filter in log stash work in synchronous or asynchronous mode?

I am facing one issue in ELK when I continuous log and tried to update some fields in log stash configuration file using Elasticsearch filter plugin its updating logs sometimes but sometimes not working, so is there and load issue or synchronous or asynchronous issue and how to resolve it for apply operation sequentially and get proper updated log in output.

Can you give an example of what you are trying to do, what is your issue and what is your logstash pipeline config?

It is confusing to understand what you are trying to do and what the issue is, also synchronous or Asynchronous in reference to what?