For Hunk , there is an add-on to query mongoDB as a virtual index. I would like to develop a similar add-on for HUNK to query a different database type. Where can I find developer resources or examples for this kind of HUNK add-on ?
I would recommend you start by downloading the java or python source codes for this sample app:
https://splunkbase.splunk.com/app/1802/
You might want to start by joining the Splunk slack channel and getting into the #appdevs subchannel, to ask there. They will have opinions for where you should start.