Postgresql vs Graph database

Just wonder why the Gen3 uses the relational database (Postgresql) to store the graph data instead of using a graph database directly?
I think that there must be reasons behind. Appreciated if anybody could share some.

Hi @hongpingliang ! Welcome to the forum!

I asked our Gen3 developers about database system choice and here is an answer:

postgres is a solid, widely used, free and open source database that the original GDC* developers had extensive experience with and understood well from both developer and operator perspectives.

*GDC is abbreviation for Genomic Data Commons, "parent" of Gen3.