不少人看似認為 Flux 是 Servlet Stack 的取代物，然而根本上是兩套不同的模型。
However, working with the reactive stream involves a bit of learning curve and ensuring that no developer ends up calling
block(). Another deal breaker might be the lack of reactive database drivers. JDBC is inherently blocking and very few other databases like MongoDB, Cassandra support reactive drivers officially at this point.