Abstraction Levels
From "user clicks Buy" to the SSD in seven levels. Solve at the highest useful level first; zoom in when necessary; know that the framework is syntax over the mechanism.
"User clicks Buy" is also a POST, a service method, a SQL transaction, a set of database pages, a filesystem write and an SSD operation. Naming the levels a problem lives on — and which one you are standing on — is how you stop mixing questions from different levels into one confused one.
Solve the problem at the highest level where it can be stated and checked, and go deeper only when that level cannot explain what you see. Most problems are solved at the top; the ones that are not announce themselves by a promise that holds and a symptom that persists.
At the architecture level the store is Frontend → Backend → Database. Zoom into Backend and it is Router → Service → Repository; zoom into Database and it is Planner → Index → Pages. Every box is a system at the next zoom, and choosing the zoom is choosing which questions are visible.
"Checkout is slow" → Backend → the database query → the B-tree → pages → the OS cache → the SSD. Each layer is a domain of its own, and the move is knowing when a layer's explanation is complete and when the next one down is required — never skipping a layer, and never going one further than the evidence sends you.
Not "how do I create an Express route" but "an HTTP request arrives, a router matches it, a handler runs, a response is written". Learn the mechanism at the level below the framework and the framework becomes syntax — learnable in an afternoon, swappable in a week.