Druid overlord read time out when submission a task via API


I have an application that submit batch ingestion task via API to overlord. The heap size of overlord is 5gb. Most of request is responded in about 0.2S as I logged them. But randomly I get read timeout for the task submission HTTP request, even when I set the timeout to 5 minutes. Is there a way that I can debug this issue? What could be the possible cause? I get this read time out when we only have 1-2 batch ingestion api call, is there any parameters that I can tune to increase the ability of overlord handling API call?