How NATS Leaf Nodes Solve MQTT Data Loss During WAN Outages at Scale

IoT devices publishing MQTT data to cloud brokers lose readings during WAN outages, a problem often discovered only weeks later when gaps appear in data logs. The two common fixes — QoS 1 persistent sessions and local Mosquitto brokers — both buffer data locally but create growing operational complexity as deployments scale to hundreds of sites. A key hidden cost is namespace drift, where different sites end up using inconsistent topic naming conventions, forcing engineers to maintain translation layers in the cloud. NATS offers an alternative via leaf nodes with JetStream enabled at each site, allowing devices to keep publishing on port 1883 while the site stores data locally and syncs with the hub when connectivity resumes. Unlike traditional bridging, this approach treats all sites as part of one network, so topic names remain consistent across every location without requiring configuration changes when new sites are added.