# preflight

Before performing a request, the library will check whether it should, based on logic and cache control.

## Should perform

Here are the conditions that would immediately cancel a request:

| Request method | Condition                                                                    | Explanation                                                                                                                                                                                                                                                                                          |
| -------------- | ---------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| GET            | An identical request (same URL, same query parameters) is already performing | We will receive the payload of the first request sooner than the payload of the second, and there is no reason they should differ                                                                                                                                                                    |
| POST           | An identical request (same URL) is already performing                        | We didn't find a way to effectively monitor POST requests. For a given resource, they have the same URL, and often the same body. However, tou can use [cache hints](/redux-rest-easy/docs/api/createresource/actionsconfig.md#properties) to differentiate multiple POST requests with the same URL |
| PATCH          | An identical request (same URL) is already performing                        | The second request might be based on outdated info, which will be updated when we receive the payload of the first request                                                                                                                                                                           |
| PUT            | An identical request (same URL) is already performing                        | Same as for PATCH                                                                                                                                                                                                                                                                                    |
| DELETE         | An identical request (same URL) is already performing                        | A resource can only be deleted once                                                                                                                                                                                                                                                                  |

## Cache control

And here are the conditions that would cancel a request based on cache control:

| Request method | Condition                                                                                                                                                                              |
| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| GET            | <p>- The exact same request has succeeded and its cache is still valid<br>- The request is about a resource/id pair which has already been retrieved, and the cache is still valid</p> |
| POST           | No cache                                                                                                                                                                               |
| PATCH          | No cache                                                                                                                                                                               |
| PUT            | No cache                                                                                                                                                                               |
| DELETE         | No cache                                                                                                                                                                               |


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