Notes :- 1. Implementation to be like [this](https://github.com/making/functional-spring-cookbook/blob/master/webfluxfn/hello-caching-caffeine/src/main/java/com/example/hellocachingcaffeine/HelloService.java). 2. [Spring Docs for Caffeine Cache](https://docs.spring.io/spring-framework/docs/current/reference/html/integration.html#cache-store-configuration-caffeine). 3. Configuration - `maxSize=1000` - config driven - `expireAfterWrite(Duration.ofSeconds(300))` - config driven 4. An API to invalidate the cache forcefully.