Delays in updates in Opensearch

We are using AWS Opensearch 1.0 as a document database to serve our retail users. We use Apache Kafka to sync Opensearch. This use-case requires Opensearch documents to be refreshed near real time for searching. We have observed that changes do not reflect for a long time.
Here is the summary of how we write and read in Openearch.

  1. Kafka event is received
  2. Parse object in the client application
  3. Client application matches received objects id to a matching Id in opensearch through the GET API.
  4. If documnt exists, update call is made, PUT.
  5. Customers are searching for data using Opensearch search API and changes are often not reflected for them.
  6. No errors or exceptions have been observed in Opensearch cluster.

Note: we have a lot of writes so a lot of indexing going on simultaneously to searches.
I suspect this is some refresh configuration that needs to be updated.