Let's start with the question, "How do you use Redis?" I'm sure most use it as a cache for the service. I hope you know that it can do more than just that. Recently, I spoke at a conference with a report on how we moved part of the data to Redis and requests fly to it in the first place. Now I want to tell you not about how we applied it, but about the fact that when working with Spring and its abstractions, you may not immediately notice the substitution.
Let's try to write a small Spring app that will use two PostgreSQL and Redis databases. I want to note that we will store in the databases not some kind of flat object, but a full-fledged object from a relational database with nested fields (inner join). To do this, we need plugins that need to be installed in Redis such as RedisJSON and RediSearch. The first allows us to store our object in JSON format, and the second allows us to search by any field of our object, even nested fields.