FAQ

Is project.yaml configuration or code? Neither — it's the table of contents of your application: topology, routing, queries, storage decisions, with your Java doing the actual work at the task nodes. The builder compiles it against your Java types and a strict linter refuses ambiguity at build time. There is no second layer of framework wiring underneath it.

What exactly is an event group? The entity your events are about — an order, a device, a user, a game. A key function derives it from each event. Groups are the unit of ordering, affinity, statistics, and (in cluster) placement. Sessions are a group's chained flows.

Why is serial admission the Core contract? Because it's the contract most event systems advertise: per-key total order, the actor model. Cold-heavy and light-flow workloads give up little to overlap — often single-digit percent. What serial costs you is hot sessions doing real per-event work, where overlap can win an order of magnitude — precisely the "your entity got busy because your business works" moment pro is priced for.

Do core, pro, and cluster give different answers? No, by construction. Every gated axis is either semantics-preserving (same answers, sooner — overlap, indexing) or a loud refusal at boot/build time (concurrent config, durability, topology). Nothing silently degrades correctness.

What happens to my spec if I downgrade? It refuses loudly at boot if it uses gated features (execution: concurrent, the HA log, router/wire config) — with the tier named in the error. Remove those declarations and the same tree runs.

Is my laptop licensed? Dev mode (the default when lounge.edition is unset) runs the complete pro capability set with a not-for-production banner. Dev and CI never need entitlement; cluster distribution and HA remain cluster capabilities. Production activation is the licensed act.

JSON or Avro? JSON on the HTTP surface everywhere — curl-able and debuggable. The native wire (cluster) carries Avro with reflection-derived schemas for machine-to-machine edges.

What survives a crash? A memory-only event store restarts empty. Database writes survive according to the database's own transaction and durability settings. Recovering Lounge event-group state requires the configured commit log and the edition that supports it; acknowledgment alone does not promise disk durability. See Durability, Clustering and HA for the exact configuration and recovery boundaries.

Can I run it outside Kubernetes? Yes — it's a JVM process. Helm charts exist for K8s; compose files exist for local clusters; a single node needs neither.

What's the licensing model? CORE source uses the Lounge Source License 1.0. Development, evaluation and staging do not require payment; production use requires the applicable license. The binary download page lists current edition prices and activation terms. Model weights have a separate Apache-2.0 license. See source and model availability and the download page.

Where do I start? Follow the first-app walkthrough, then add one business operation and tests for its success and failure cases.