What would happen if a user tries to access a storage account using an expired access key?

When a user attempts to access a storage account using an expired access key, access will be denied. This is because access keys in Azure storage are used as security credentials to authenticate requests. If an access key has expired, the storage service no longer recognizes it as a valid credential, thus preventing any access to the data or operations tied to that storage account.

This mechanism is in place to enhance security, ensuring that only valid, current keys can access resources. It is the responsibility of users or administrators to manage and regenerate keys as needed to maintain access to their resources.