Vert.x 의 Hazelcast 사용이유
http://www.cubrid.org/blog/dev-platform/understanding-vertx-architecture-part-2/
Why is Hazelcast Used?
Vert.x uses Hazelcast, an In-Memory Data Grid (IMDG). Hazelcast API is not directly revealed to users but is used in Vert.x. When Vert.x is started, Hazelcast is started as an embedded element.
Hazelcast is a type of distributed storage. When storage is embedded and used in a server framework, we can obtain expected effects from a distributed environment.
The most popular case is session data processing. Vert.x calls it Shared Data. It allows multiple Vert.x instances to share the same data. Of course, additional RDBMS, instead of Hazelcast, will bring the same effect from the functional side. It is natural that embedded memory storage can consistently provide results faster than remote RDBMS. Therefore, users who need sessions for e-commerce or chatting servers can build a system with a simple configuration by using only Vert.x.
Hazelcast allows a message queue use without additional costs or investments (without server costs or monitoring of message queue instances). As mentioned before, Hazelcast is a distributed storage. It can duplicate a storage for reliability. By using this distributed storage as a queue, the server application implemented by using Vert.x becomes a message processing server application and a distributed queue.
These benefits make Vert.x a strong framework in a distributed environment.