Save up to 55 percent on your Azure Cache for Redis premium tier usage by pre-purchasing reserved capacity for one year or three years. This reservation discount will automatically apply to your matching resources, so there’s no need to make changes to them to receive the reservation discount. Azure Cache for Redis reservations include instance size flexibility enabled by default, which means that the reservation will continue to apply to your Azure Cache for Redis premium usage even if you were to resize the cache. Should your requirements change in the future, you will be able to exchange or refund these reservations.
Purchase reserved capacity from the Azure portal today, or read the documentation.