<!--
title: Persist Only Settled Queries
domain: app-frameworks
topic: Concurrency
language: Markdown
source: tanstack/query
updated: 2025-12-26
url: https://awesomereviewers.com/reviewers/query-persist-only-settled-queries/
-->

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When using async/concurrent flows (streaming, dehydration/rehydration, optimistic updates), ensure you never persist “in-flight” async state and you always return promises from async callbacks.

1) Don’t persist promises during streaming/dehydration
- If a query might still be pending, configuring persistence to store only settled/resolved outcomes prevents serialization issues when pending work is dehydrated and streamed.

```tsx
<PersistQueryClientProvider
  client={queryClient}
  persistOptions={{
    persister,
    // Persist only queries that have resolved (not pending promises)
    dehydrateOptions: { shouldDehydrateQuery: defaultShouldDehydrateQuery },
  }}
>
  {children}
</PersistQueryClientProvider>
```

2) Don’t drop promise lifecycles in concurrency callbacks
- For concurrency-related callback hooks (e.g., mutation lifecycle handlers) that trigger async work, write them in a way that returns the promise (consistent concise arrow syntax is preferred).

```ts
useMutation({
  onSettled: () => queryClient.invalidateQueries({ queryKey: ['todos'] }),
});
```

Practical checklist:
- Any persistence/dehydration layer: allow only resolved/errored (settled) query results to be stored.
- Any callback that triggers async operations: return the promise so downstream orchestration/lifecycle expectations remain correct.
{% endraw %}