Apache Druid

I ask this because more tasks seems to help speed up the ingestion, but I am not sure why.

I have tried increasing recordsPerFetch very high with a lower level tasks, but this does not seem to help.

For instance with these params, my stream did not lag
```"taskCount": "17",
"recordsPerFetch": 150,
"fetchDelayMillis": 6500```
While these params did lag
```"taskCount": "6",
"recordsPerFetch": 450,
"fetchDelayMillis": 6500```
despite there being more total throughput implied by my choice of taskCount, recordsPerFetch and fetchDelayMillis. I also was not receiving too many throughput errors in either case. Also we are not seeing any cpu/memory issues on the middle manager.

Could there be another parameter serving as a bottleneck for pulling data through a single task?