Description

Microsoft is retiring Azure Cache for Redis version 4 starting from June 30, 2023. Redis is used for the session state storing in Sitecore. Microsoft recommends upgrading all Azure Redis deployments to version 6 before that time. All deployments that use Azure Cache for Redis version 4 will be upgraded automatically after the deadline.

Microsoft has stated that version 6 is compatible with version 4, and no changes are required in client applications to ensure compatibility. At this time, no compatibility issues have been observed on Sitecore instances when using Azure Cache for Redis version 6.

For further information and questions, including availability of the Redis Cache during the upgrade process, refer to the official Microsoft documentation: 
https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/cache-retired-features

Solution

To upgrade Azure Cache for Redis, consider one of the following options:

• Update Azure Cache for Redis manually, using the Azure Portal:
  • Navigate to the Azure Cache for Redis and select Advanced settings.
  • Click the notice at the top of the window about Redis version 4 retiring and follow the instructions provided to change Redis version to the latest version 6.
• Set up Scheduled updates to allow Redis to upgrade during a designated maintenance window using the Azure Portal:
  • Navigate to the desired Azure Cache for Redis and select Scheduled update.
  • Setup the desired upgrade window.
  • It is recommended that the Scheduled updates be disabled after the upgrade has been completed to prevent unplanned upgrades in the future.
• Take no action and allow the cache to upgrade itself on the upgrade deadline.