Putting it together: multiple-choice review
Cross-track multiple-choice synthesis: read a frontend symptom, locate the layer that actually owns the bug, and pick the fix that does not just mask it.
Every question here crosses two or three units. The skill the capstone tests is not recall of one layer — it is reading a symptom and naming the lowest layer that owns it, because that is where the durable fix lives.
Work through each question before reading the answers — the diagnostic muscle only sharpens when you commit to a layer first.
Confirm you can trace a frontend symptom down the cascade — state shape, fetch graph, tokens, monorepo boundaries, splitting, pipeline — and reject fixes that optimise a layer above the real cause.
A dashboard janks on every keystroke in its search box. A teammate files a ticket to code-split and lazy-load the charts. What is the senior read?
A product page renders a skeleton, then JS hydrates, then it fetches the user, then the cart, then recommendations — each waiting on the previous. LCP is 4.8 s. Which layer owns this, and what is the fix?
Marketing asks for a rebrand: a new brand color plus a dark mode. The codebase has the brand hex hardcoded across ~300 components. What does this reveal, and what is the structural fix?
CI takes 15 minutes for a one-line change in one of 12 packages because everything imports one giant shared package. What attacks the root cause?
You are handed a new frontend to review. In which order does a senior evaluate the layers, and why that order?
A heavy charting library loads on first paint of every route even though most users never open the analytics tab, and a screen-reader user reports the date-picker inside it traps focus. Which two-layer fix is right?
The through-line across the track is one decision tree. Where state lives sets the re-render blast radius; the fetch graph owns LCP; tokens decide whether a rebrand is a value swap or a file hunt; monorepo boundaries are the build-time multiplier; splitting and the pipeline are the cheapest layers. Every question above is the same move — read the symptom, drop to the lowest layer that owns it, and reject any fix that optimises a layer above the cause. Now when you see jank, a slow LCP, or a 15-minute CI build, you know where to look first.
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