Mercury Composable for Java

Mercury Composable lets you build backend applications as composable, event-driven systems — and, increasingly, as Active Knowledge Graphs you evolve by editing a model rather than rewriting code. Functions are fully decoupled — they know each other only by route name, wired through event envelopes — so orchestration is configuration, not code. It runs on Java 21 virtual threads, so straightforward synchronous code performs on par with reactive. The event-driven core descends from the Scala/Akka actor model, realized on the Eclipse Vert.x event bus.

New here? Start with Getting Started — it opens with a 5-minute quickstart.

A layered ascent

Mercury grew in three layers. Each builds on the one beneath it, and you can mix them in a single application — drop down a layer exactly where you need more control, and no further.

Layer You express behavior as… What you write
Event-driven
Platform Core		 decoupled functions reacting
to events		 Java functions,
addressed by route name
Composable
Event Script		 YAML flows that choreograph
functions		 ~50% config,
50% code
Semantic
Active Knowledge Graph		 a graph whose nodes execute
during traversal		 a model —
little or no code

Knowledge Graph as application

The newest layer is a paradigm shift: model business intent, enterprise knowledge, and system behavior as one executable Active Knowledge Graph. Behavior runs as the graph is traversed, so changing what a system does means refining the model, certifying it, and deploying the updated model — not rewriting and redeploying code. Humans and AI companions co-author the same model.

Building with an AI agent

Mercury's DSLs ship agent-ready specifications — a rule-based grammar plus a machine-readable catalog — so an AI agent can generate correct artifacts deterministically, without inferring from examples or reading engine source:

A machine-readable map of the whole site lives at llms.txt.

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