Most, if not all, applications need to store some data, some applications far more than others. By holding this book in your eager hands and starting to flip through its pages, it might be safe to assume you have previously worked to architect, develop, or support applications more towards the latter end of that scale. We could imagine that you are all too painfully familiar with the common pitfalls and issues that tend to crop up around scaling or distributing your data layer. But to make sure we are all up to speed, in this chapter, we shall examine: