URL State & Navigation

Most candidates name local, global, and server state and stop there. Senior answers add URL state: the layer that makes a view shareable, bookmarkable, back-button correct, and server-renderable.

This module covers what belongs in the URL versus a store, encoding filters and pagination in search params, deep linking, scroll restoration, optimistic navigation, and how URL state interacts with React Query cache keys.

You will learn the practical mechanics too: useSearchParams and router.replace vs push, avoiding history spam while typing, debouncing URL writes, and keeping SSR and client state in sync without hydration mismatches.

Interviewers use this to separate people who have shipped real dashboards from people who have only built demos: filters that vanish on refresh are the classic tell.

Phase 3 (Week 3) of the interview roadmap. Senior Track spans modules 1–19; the Staff Track starts at module 20.