Hands-On Lab and Phase Exit Prove that you understand server-state ownership before moving on
Phase 22 - TanStack Query Volume 06 - Professional Frontend
Hands-on lab: migrate the Task collection Complete the lab in order. Do not start by copying the final snapshot. The goal is to feel which manual responsibilities disappear as TanStack Query takes them over.
Level 1 - Provider Install the locked packages, create getQueryClient(), mount QueryClientProvider, and confirm Devtools can see an empty cache.
Level 2 - Read Create taskKeys and taskListOptions. Replace the client-side manual fetch lifecycle with useQuery. Verify first load, cached navigation, background refetch and error UI.
Level 3 - Pagination Drive page/status/search from URL search parameters. Put the normalized query object into the key. Use keepPreviousData and verify page transitions no longer collapse into an empty loading state.
Level 4 - Mutations Move create and update network state to useMutation. Invalidate Task lists after successful writes. Do not implement optimistic updates yet.
Level 5 - Production App Router Prefetch the current task-list query from the Server Component and hydrate it into TasksScreen. Confirm the first render contains data while the browser still owns later revalidation.
Security verification Load Task data as user A, sign out, clear the query cache, sign in as user B and verify no prior cached Task content is displayed.
Phase exit checklist Check Required result
Pagination URL owns page/filter state; cache owns server result
You should be able to explain why a Task query refetched, why it did not refetch, which cache entry a page uses, and which queries a successful mutation invalidates without guessing.
Required evidence Do not mark the phase complete just because the page renders. Capture evidence showing two distinct pagination keys, mutation-driven invalidation, background refetch that preserves the table, and an empty cache after logout.
Common mistakes to deliberately test Mistake Observed symptom
Invalidate only one exact page Other Task list views stay stale after create
Create QueryClient during every Cache disappears unpredictably client render
Copy query.data into component Refetched cache and local copy diverge state
TanStack Query is a server-state synchronization system, not merely a fetch helper. Cache identity, freshness, invalidation, and mutation semantics are the core model.
Restate the goal of “Hands On Lab and Phase Exit” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: component → query key → cache state → fetch/mutation → reconciliation. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: TaskFlow query/mutation layer with stable keys, list/detail caching, invalidation, filters, and debugging via devtools/logs.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
export const taskKeys = {
all: ["tasks"] as const,
list: (filters: TaskFilters) => ["tasks", "list", filters] as const,
detail: (id: string) => ["tasks", "detail", id] as const,
};Do not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Return to the nearest observable boundary: input, network, process log, database, or rendered UI. Compare actual evidence with the predicted path.
Change one variable at a time and reproduce the original failure after the fix; otherwise you have correlation, not diagnosis.
Without copying the final source, create a second small scenario that applies “Hands On Lab and Phase Exit” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Add pagination/filter URL state and inspect how query keys prevent cross-filter cache corruption.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Treating staleTime as data lifetime/deletion
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.