The NATS Execution Engine (we'll just call it Nex most of the time) is an add-on to NATS that overlays your existing NATS infrastructure, giving you the ability to deploy and run workloads.
When we build applications that rely on NATS as a backbone, we get to leverage communications, global reach, reliability, performance, and even services like JetStream, Key-Value stores, and Object Stores. However, up until Nex, we haven't been able to use that infrastructure as a deployment target.
The NATS execution engine is currently experimental. The documentation, feature set, and any APIs are likely to change frequently.
While you can build virtually any kind of application with Nex, the core building blocks are made up of two fundamental types of workloads: services and functions.
Within the context of Nex, a service is just a long-running process. When it is deployed, it is launched with a given environment and runs continually until terminated. Typical examples of service-type workloads are web servers, monoliths, API endpoints, and applications that maintain long-running subscriptions to NATS subjects.
Nex services are statically-linked, 64-bit linux (elf) binaries. However, you can also create your own root file system with a container daemon installed and run OCI images as well.