Letting these SaaS offering redefine referential data without integrating and sharing a common primary key is a disaster that should be avoided at all costs. No one wants to manually maintain two employee or customer lists in 2 different systems, and worst: having to do fuzzy matching when bringing their HR data back into their warehouse.
further denormalization: maintaining surrogate keys in dimensions can be tricky, and it makes fact tables less readable. The use of natural, human readable keys and dimension attributes in fact tables is becoming more common, reducing the need for costly joins that can be heavy on distributed databases. Also note that support for encoding and compression in serialization formats like Parquet or ORC, or in database engines like Vertica, address most of the performance loss that would normally be associated with denormalization. Those systems have been taught to normalize the data for storage on their own.
Eat your hard-boiled eggs sporadically throughout the day, but save one. Do not take any breaks except to mix protein shakes. Remember that you should be consuming one gram of protein per pound of body weight, or per line of code written — whichever is greater.