[4/40 things about data] The second most important rule of working with data: the fastest data is the one you don’t read

As simple as it sounds, most people forget about using one of the most important database features: indexes. Well, you also need to think about what’s the data you actually need, a lot of apps are full of select * from table.

The problem is, as your system grows, so does the amount and complexity of queries. Knowing what data you need becomes harder. To avoid that you need… yes, data about how you query your data.