Druid Performance

I am using druid with tranquility-kafka realtime ingestion no batch ingestions on a T2.large machine. I am facing some problems.When I run group by a query on druid It throws an exception saying increase druid .processing.buffer.sizeBytes. I have increased the same then I start getting the results but now I see more pending tasks on overlord console, earlier it was working fine.
Below is my configurations.
Historical runtime

events.txt (4.62 MB)

any suggestions ?