Also keep in mind that learning to "organize your data for fetching" is not necessarily something you can do before you start your project. Many (most?) times you can't predict which data access patterns will be most common and benefit from using Redis, etc.

Starting with a "slower, but flexible" datastore like a traditional relational database, monitoring which access patterns need a boost, and then optimizing or introducing a new datastore is almost always a solid plan of attack.