How to minimize peon heap memory consumption while ingestion?

Hi everyone,
I need to ingest data into hundreds of Druid datasources from Kafka using Tranquility. Each datasource has about 20 dimensions and 10 measures. 1 to 100 messages/second depending on datasource.
My current objective is to minimize heap memory required for each peon. Please let me know your ideas about how to configure middle manager to achieve this.