Understanding Redis inside Spring Boot - spring

Question

I have a Spring Boot application, where I need to get data from a table when the app initializes.
I have a repository with the following code:
#Repository
public interface Bookepository extends JpaRepository<Book, Integer> {
Proveedor findByName(String name);
#Cacheable("books")
List<Proveedor> findAll();
}
Then from my service:
#Service
public class ServiceBooks {
public void findAll(){
booksRepo.findAll();
}
public void findByName(String name){
booksRepo.findByName(name);
}
}
And then I have a class that implements CommandLineRunner:
#Component
public class AppRunner implements CommandLineRunner {
private final BookRepository bookRepository;
public AppRunner(BookRepository bookRepository) {
this.bookRepository = bookRepository;
}
#Override
public void run(String... args) throws Exception {
bookRepository.findAll());
}
}
So here,when the application initializes, it queries to the Books table and caches the result. Inside the application each time I call find.all(), the cache is working, and I get the data from my cache.
So here are my 2 questions:
About Redis, I am not using Redis and I am doing database cache without any problem. So, where does Redis fit into this approach? I don't understand why everybody uses Redis when cache is working without needing other libraries.
When I call findByName(name), is there any chance to execute that query over the data I already have cached? I know I can have a cache on that method, but the cache will save data each time I search a particular name. If a name is searched for the first time, it will go to the database for that value. I don't want that, I would like that Spring performs the query using the data from the first cache where I have all Books.

Answer 1

The answers to your question
Redis avoids the DB call as it stores your response in Memory. You can use #cacheable even in controller or service. If you use #cacheable in controller, your request will not even execute the controller method, if it is already cached.
for FindByName, Redis provides a nice way to store the data based on keys.
Refer the link Cache Keys.
Once you request by Name, it will get the data from DB, the next time you request with same name, it will get from cache based on the key.
Coming back to your question, NO you should not do a search on your cached data, as caches are highly volatile, you cannot trust the data from cache. also searching through the cached data might affect the performance and you might need to write lines of unneeded additional code.

Answer 2

Spring boot manages the cache per application or per service. When you are using multiple instance of a service or app then certainly you'll want to manage the cache centrally. Because per service cache is not usable in this case because what one app caches in its own spring boot is logically not accessible by another apps.
So here Redis comes into picture. If you use Redis, then each instance of service will connect to the same Redis cache and get the same result.