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# Storage

The `Storage` utility provides a string-backed key-value contract for Tempo features. Use
[`Storage.memory`](/tempo/utilities/Storage.memory) for process-local data or
[`Storage.from`](/tempo/utilities/Storage.from) to wrap another store.

## Contract

```ts
type Storage = {
  compareAndSet?(
    key: string,
    expected: string | null,
    value: string,
  ): MaybePromise<boolean>
  getItem(key: string): MaybePromise<string | null | undefined>
  removeItem(key: string): MaybePromise<void>
  setItem(key: string, value: string): MaybePromise<void>
}
```

### `compareAndSet`

Atomically replaces the current value when it equals `expected`. Multisig coordination uses this
method when available to preserve approvals submitted concurrently.

Without `compareAndSet`, multisig coordination falls back to `getItem` and `setItem`. Concurrent
submissions can overwrite an approval, so an owner may need to submit the approval again.

## See Also

* [`Storage.from`](/tempo/utilities/Storage.from)
* [`Storage.memory`](/tempo/utilities/Storage.memory)
* [`Storage.session`](/tempo/utilities/Storage.session)