Publish a message to a subject and every subscriber hears it. That is core NATS: a small, fast messaging system for connecting services with publish-subscribe and request-reply, without much ceremony. NATS Over Easy is the relaxed side of it, where wiring one service to another takes a subject name and a few lines.

Know the delivery guarantees. Core NATS is fire-and-forget, so a subscriber that is offline misses the message. When you need persistence, acknowledgements and replay, reach for JetStream, which stores messages in streams that consumers read at their own pace.