Hello Tandon, Ankur,
Welcome to the Microsoft Q&A and thank you for posting your questions here.
I understand your concerns to scale the storage capacity and change accordingly with a similar specification to a lower tier.
You can scale both the memory and performance characteristics of your cache in Azure cache for Redis, but you cannot directly adjust storage capacity independently for these settings.
This link https://azure.microsoft.com/en-us/pricing/details/cache - explains the features and limits of available tiers and help you to choose the right configuration for your needs.
Also, on how to resize your cache and switch between different tiers - use this link for more detailed steps - https://zcusa.951200.xyz/en-us/azure/azure-cache-for-redis/cache-how-to-scale
I hope this is helpful! Do not hesitate to let me know if you have any other questions.
Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful