NATS & JetStream Distributed Messaging AI Skill Guide

Overview & Engine Architecture

Core NATS is fire-and-forget pub/sub (at-most-once on lossy paths). JetStream adds persistence, replay, consumer acks, KV/Object stores, and Raft-replicated metadata. Publish deduplication (Nats-Msg-Id + stream duplicate_window) prevents duplicate records in the stream; consumer delivery remains at-least-once unless handlers are idempotent and ack timing is correct.

Publishers (TLS, creds/JWT)
    -> NATS cluster (4222 client / 6222 route)
        -> JetStream streams (limits/workqueue/interest retention)
        -> consumers (pull preferred in prod)
Subscribers ack/nak/in-progress

When to use / when not to

Use when