[pm90]

One thing to note is that the singular database used for answering business questions is often not customer facing, and thus does not have as strong reliability guarantees (In my experience). Most of the business analytics happens asynchronously (etl pipelines everywhere).

I'm not sure how to avoid this. The need to answer business question favors a single, queryable DB whereas the need to keep applications siloed and abstracted away favors multiple application data stores.