Docker isn't really required for this. Any in memory db will provide good contract verifications. And a simple alpha/beta/gamma setup with the end database can get you the rest of the way there.
Docker can be a bit of a better option... Unless you're using the same database software for the in-memory operations as the actual deployment. Or aren't using many specific features the rdbms you have chosen (stored procedures, triggers, virtual fields, etc). Not that I'm a fan of triggers and prefer direct table access over SP, but virtual fields are GREAT during transitional changes.
It also generally requires an abstraction between the DB variants.
Agreed. In the old world, this is what an alpha/beta/gamma environment could help test against. The in memory could be used to make sure your units and overall components were correctly specified. The actual installs of the DB software to isolated schemas were where you made sure you integrated with the DB correctly.
That all said, I did not mean this to be that Docker doesn't provide some value. Just pointing out it is not a prerequisite. If that makes sense.
