Every request your app serves is a chance to do less work. Caching is just the art of not redoing work you already did. Sounds simple. It isn’t — there’s a whole stack of places you can stash data, each with its own rules, and picking the wrong layer (or the wrong expiry) costs you either stale bugs or a slow site.
I’ve spent enough hours staring at a page that “should have updated” but didn’t, only to realise the answer was cached three layers deep. So let me walk through every place you can cache — from the user’s browser all the way down to compiled bytecode on your server — and where each one bites you.
Everyone talks about SOLID principles. Your senior dev mentions them in code review. Your architecture docs reference them. But why do actual projects become unmaintainable garbage despite teams “knowing” SOLID? The answer: understanding SOLID and actually building with it are two completely different things [1].
Most developers learn about SOLID early, nod along, then immediately violate these principles the moment a deadline hits. Let me show you where the rubber meets the road — and why it’s harder than it sounds.