Should Hub have a relational database backend

This keeps coming up so I want to address it. Sounds we're mostly expecting we'll eventually add an RDMS but for me, this has always been an architectural antipattern. (Admittedly I'm not a front end dev.)

At Amazon, traditional RDMS's were expressly forbidden for any production workloads that needed to scale, so I'm admittedly pre-biased against RDBM's and OLTP use cases for the Hub.

Would be helpful to understand what requirements we feel like would be benefited from an RDMS.

If we do have use cases that will require RDMS backend, I'd like to understand those better so I can update my own expectations and so we can start designing the long-term solution that we need.