>>the db was so well abstracted, they managed to swap these out with no need to rewrite any application code What were the reasons for the swap and what were t

>>the db was so well abstracted, they managed to swap these out with no need to rewrite any application code What were the reasons for the swap and what were the outcomes of it besides that it actually happened? Costs, performance, scalability etc? I think hardly anyone would argue that those transitions are impossible, because they are indeed possible. The main question is usually if your abstraction can leverage the benefits of underlying implementation or it is just a common denominator. I can imagine a clever technical strategy in a startup, foreseeing future growth and starting with a simple DB before moving to a more complex in maintenance but scalable solution. This may work. Often it doesn't.