Updated production setup documentation

Author: subkanthi

doc/production_setup.md

@@ -65,6 +65,11 @@ The maximum number of rows that the connector fetches and reads into memory when
 
 **snapshot.max.threads**: Increase this number from 1 to a higher value to enable parallel snapshotting.
 
+**Single Threaded (Low Memory/Slow replication)**:
+By setting the `single.threaded: true` configuration variable in `config.yml`, the replication will skip the sink connector queue and threadpool
+and will insert batches directly from the debezium queue.
+This mode will work on lower memory setup but will increase the replication speed.
+
 ## PostgreSQL Production Setup
 
 One of the common problems with PostgreSQL is the WAL size increasing.