IoT telemetry with MQTT at scale

Field IoT deployments mean planning for power cuts, cellular fallback and technicians who may not have a laptop on site. MQTT is our default transport because it is lightweight, pub/sub native and tolerant of intermittent connections.

Hardware choices

ESP8266 remains cost-effective for stationary sensors. We add deep-sleep cycles and supercapacitor buffers for brief outages. For mobile assets, we use ESP32 with LTE modules when budget allows.

MQTT topic design

Hierarchical topics like `site/{id}/node/{id}/telemetry` keep ACL rules simple. QoS 1 for telemetry, QoS 0 for heartbeat pings. Retained messages only for config, never for high-frequency data.

Dashboard requirements

Operators need mobile-friendly dashboards. We build with Astro or React, WebSocket bridges to the broker and alert thresholds that push to email or SMS because those are channels people actually check.

Security

TLS on MQTT (port 8883), per-device credentials and broker ACLs that isolate tenants. No anonymous publish.

Takeaway

The Smart Traffic Control project proved this architecture works at intersection scale. The same patterns apply to tank monitoring, cold chain and energy metering.