Server side caching with multiple datasets

Hello community!
There is an app which analyse two main entities, say posts and their comments. Typical scenario:
User requests posts(<1K) and starts analyzing associated comments (100K+). Up until now i used Stores to share the between callbacks, but now, as data grows, experiencing with performance issues. Never worked with Redis and wonder how to use properly.
choosing between two options:

  • save returned datasets with keys "posts" and "comments"
  • save each post separatly with key like 'post_id'. For comments "post_id":{comment_1,comment_2 etc}

Which of those approaches is correct (if any)?

Sorry if smth similar has been already asked, didn’t find anything relevant
Thank you