Five years ago when I started tracking media buzz around stateful architectures, I’d see a few articles every month about running stateful containers. That's about when Caitie McCaffrey first shared this awesome presentation about building scalable stateful architectures. Since then, the dominant software paradigm has become functional application design. The actor model and other object-oriented paradigms are still in use, but database-centric RESTful architectures are standard means of building web applications today.
However, the tides are beginning to shift. Due to innovations like the blockchain, growing demand for real-time applications, the digitization of OT assets, and the proliferation of cheap compute resources at the network edge; there’s renewed interest in decentralized application architectures. As such, there’s also been increased focus on stateful applications. For example, at least five Apache Foundation projects (Beam, Flink, Spark, Samza, and TomEE) are touting statefulness as a benefit today. Modern applications communicate across multiple application silos and must span real-world machines, devices, and distributed data centers around the world. Stateful application architectures provide a way to abstract away the logistical effort of state management, thereby reducing development and management effort necessary to operate massive-scale distributed applications.
Build a Scalable, Stateful To-Do List in 15 Minutes or Less
For the rest of this post, I want to disprove the notion that building scalable, stateful applications is a task too complex for everyday Java developers. In order to illustrate how easily a stateful application can be setup, we’ll walk through a tutorial for building a simple to-do list using the Swim platform. You can find all the source code for the to-do list tutorial here on GitHub.