How to throttle shard replication process?

Elastic Stack Elasticsearch
1

I disabled shard replication (by setting number of replica to 0) when I loaded a tons of data into elasticsearch. After the load finish I enabled the replication (by setting the number to 2). Now I can see elasticsearch started transferring data to replication shards.

At this moment when I query the index or send bulk indexing again, I got "Read timed out. (read timeout=30))". As you can see I've increased the time out to 30 seconds. I can see the cluster is transferring replication data from the head plugin. So I'm guessing it's utilizing all the thread and hence blocking any new queries.

Is there anything I can do to make rooms for searching?

Here's my cluster settings:

{
   "persistent": {
      "indices": {
         "store": {
            "throttle": {
               "type": "merge",
               "max_bytes_per_sec": "100mb"
            }
         }
      }
   },
   "transient": {
      "cluster": {
         "routing": {
            "rebalance": {
               "enable": "none"
            },
            "allocation": {
               "enable": "all"
            }
         }
      },
      "threadpool": {
         "bulk": {
            "queue_size": "1000",
            "size": "16"
         },
         "index": {
            "queue_size": "1000",
            "size": "16"
         }
      },
      "indices": {
         "store": {
            "throttle": {
               "type": "none"
            }
         }
      }
   }
}

Thanks in advance!