Web / TanStack Interview Questions

What are the most common TanStack Query mistakes in Vue and how do you avoid them?

Knowing what not to do is as important as knowing the API. These patterns trip up most developers new to TanStack Query in Vue.

Common Mistakes
Mistake	Problem	Fix
queryKey not including all query variables	Stale data served when variable changes	Add every queryFn variable to the key
Non-reactive queryKey in Vue	Query doesn't re-run when props change	Wrap queryKey in computed() when it reads reactive state
Server state in both TanStack Query and Pinia	Two sources of truth — sync bugs	Use TanStack Query as the single source for server data
New QueryClient per component	Each component gets its own empty cache	Create QueryClient once in main.ts
staleTime=0 for slow/static data	Unnecessary refetch on every window focus	Set staleTime to match data update frequency

// WRONG: non-reactive key â captured once at setup, never updates
const { data }=useQuery({
  queryKey: ["user", props.userId],  // plain read, not reactive
  queryFn:  ()=>fetchUser(props.userId),
})

// CORRECT: reactive via computed()
const { data }=useQuery({
  queryKey: computed(()=>["user", props.userId]),
  queryFn:  ()=>fetchUser(props.userId),
})

// WRONG: duplicating server state into Pinia
const { data:user }=useQuery({
  queryKey: ["user",1],
  queryFn:  fetchUser,
  onSuccess: u=>userStore.setUser(u), // unnecessary sync â two sources of truth
})
// CORRECT: read data directly from useQuery wherever needed

Take quiz

Why must queryKey be wrapped in computed() in Vue when it depends on a prop?TypeScript requires it

✗ Try again.

A plain prop read is captured once at setup; computed() creates a reactive reference TanStack Query can watch — without it the query never re-runs when the prop changes

✓ Correct! Well done.

TanStack Vue adapter only accepts computed refs

✗ Try again.

Props are immutable in Vue

✗ Try again.

What is the problem with keeping server state in both TanStack Query and Pinia?Pinia and TanStack Query can't coexist

✗ Try again.

Creates two sources of truth for the same data — they can drift out of sync, requiring manual synchronisation code that becomes a maintenance burden

✓ Correct! Well done.

Pinia is not reactive enough

✗ Try again.

TanStack Query won't fetch if Pinia store is present

✗ Try again.

More Related questions...

What is TanStack and what problem does it solve for frontend developers? What is TanStack Query and what core problems does it solve over plain fetch in Vue? How do you set up TanStack Query in a Vue application? How should you design queryKeys in TanStack Query and why do they matter? What is the difference between staleTime and gcTime in TanStack Query? What are the most useful useQuery options beyond queryKey and queryFn in Vue? What is useMutation and how do you use it to submit data in Vue? How do you write dependent (sequential) queries in TanStack Query with Vue? How do you implement pagination and infinite scroll with TanStack Query? How do you prefetch data in TanStack Query to speed up navigation? What is TanStack Router and how does it differ from Vue Router? How do you define routes in TanStack Router with Vue? How do you use URL search params as typed state in TanStack Router? What are route loaders in TanStack Router and how do they integrate with TanStack Query? What is TanStack Table and how do you create a basic table in Vue? How do you add client-side sorting and column filtering to a TanStack Table in Vue? How do you implement pagination with TanStack Table? How do you add column visibility toggling and row selection to a TanStack Table? What is TanStack Form and how do you build a basic form in Vue? How do you add synchronous and asynchronous field validation in TanStack Form? How do you manage dynamic field arrays in TanStack Form? What is TanStack Virtual and when should you use it? How do you handle variable-height rows in TanStack Virtual? How do you combine useInfiniteQuery with useVirtualizer for an infinitely scrolling virtualised list? How do you implement optimistic updates with TanStack Query? What are the status and fetchStatus values in TanStack Query v5 and how do they drive UI? How do you create links and perform programmatic navigation in TanStack Router with Vue? How does TanStack Router handle route-level errors and loading states? How do you integrate TanStack Table with server-side sorting, filtering and pagination? What developer tools does TanStack provide and how do you add them in Vue? What are query key factories and why are they recommended for large Vue apps? How do you implement cross-field (form-level) validation and handle submission in TanStack Form? How do you pass variables to a mutation and use them across lifecycle callbacks? How do you virtualise a horizontal list or two-dimensional grid with TanStack Virtual? What are the most common TanStack Query mistakes in Vue and how do you avoid them? How do you implement protected routes and auth redirects in TanStack Router? How do you render custom Vue components inside TanStack Table cells? How do the TanStack libraries compose into a full application stack, and what is TanStack Start?

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Web / TanStack Interview Questions

What are the most common TanStack Query mistakes in Vue and how do you avoid them?

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