Elasticsearch Sink Connectors - Synchronous mode slowing down connector

Hi Team,

I am using Elasticsearch sink connector to push data from multiple kafka topics to single elasticsearch index. As I would need to achieve it with regex in elasticsearch connector, it is making elasticsearch sink connector synchronous which is resulting in slower performance.

Another option I see as to redirect all these topic events to single topic and map it with index so that performance would be greater as compared to current performance. But As it will be asynchronous, is there a chance of data loss? Is there any other way to increase performance ensuring no data loss? What is the delivery semantics while sink connector is asynchronous?

Kindly help here.