I know the clustering for DB is built-in only on the Magento 2 commerce, but I want to know could I build this feature on the Magento 2 community?
Yes - you are correct , this feature is only available in commerce edition (Enterprise edition).
Because in enterprise edition magento has developed module for this functionality called split:db
so if you wanted to achieve this in open source edition , then you must need to create a custom module for that.
Well based around my experience and the research i have done so far , i am not able to find any third - party extension which does the same functionality which magento EE split database module do . in-fact i am not able to found any module for that .
so my answer is yes - as of now there is no open source module to achieve that for magento 2.
might be you will find for Magento 1 but magento2 there is no module.
hope it helps ! if its helps you please click on kudos and accept as solution