{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T13:19:41Z","timestamp":1788268781755,"version":"build-2803163510"},"reference-count":39,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T00:00:00Z","timestamp":1788220800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"AGH University of Krakow"},{"id":[{"id":"https:\/\/ror.org\/00bas1c41","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper presents the design and experimental characterization of a distributed ESP32\/MicroPython edge\u2013cloud sensing system with packet-level latency decomposition. Sensor nodes transmit periodic telemetry to an ESP32 gateway over ESP-NOW; the gateway appends reception and MQTT-publication timestamps and forwards records through a local Mosquitto bridge v2.1.2, EMQX Cloud v5, Telegraf v1.36.0, and InfluxDB Cloud Serverless (Storage Engine Version 3). A three-probe two-way gateway-referenced synchronization procedure provides corrected sender timestamps while exposing an interval-based synchronization-uncertainty diagnostic. The bridge-assisted campaign comprised three independent 30 min repetitions with one, three, and five active nodes. Across runs, mean gateway-referenced node-to-gateway latency was 23.17 \u00b1 0.13 ms, 24.13 \u00b1 0.12 ms, and 24.84 \u00b1 0.47 ms, respectively; the corresponding p95 values were 28 ms, 33 ms, and 37\u201338 ms. Mean gateway-processing latency remained nearly unchanged at 13.31\u201313.46 ms. Exact full-run database-visible PDR was 100% in all one-node runs, 99.28\u201399.88% in the three-node runs, and 96.75\u201397.05% in the five-node runs. Independent GPIO\/oscilloscope validation showed a reproducible positive software-to-hardware difference of 12.132 \u00b1 1.819 ms across run means, so the local metric is interpreted as a gateway-referenced application-level delivery metric rather than unbiased physical one-way radio latency. Relative to aggregate end-to-end reporting, the instrumentation separates local, gateway, and downstream ingestion contributions rather than claiming a universally faster transport method. Quantitative performance and scaling claims are confined to the evaluated bridge-assisted configuration and controlled indoor periodic workload.<\/jats:p>","DOI":"10.3390\/s26175555","type":"journal-article","created":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T12:41:18Z","timestamp":1788266478000},"page":"5555","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Characterization of Latency Sources in a MicroPython-Based ESP32 Edge\u2013Cloud Sensor Network"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7291-6136","authenticated-orcid":false,"given":"Katarzyna","family":"Smelcerz","sequence":"first","affiliation":[{"name":"AGH University of Krakow, al. Mickiewicza 30, 30-059 Krakow, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"637","DOI":"10.1109\/JIOT.2016.2579198","article-title":"Edge Computing: Vision and Challenges","volume":"3","author":"Shi","year":"2016","journal-title":"IEEE Internet Things J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1109\/MC.2017.9","article-title":"The Emergence of Edge Computing","volume":"50","author":"Satyanarayanan","year":"2017","journal-title":"Computer"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1275","DOI":"10.1109\/JIOT.2018.2805263","article-title":"Edge Computing for the Internet of Things: A Case Study","volume":"5","author":"Premsankar","year":"2018","journal-title":"IEEE Internet Things J."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Plauska, I., Liutkevi\u010dius, A., and Janavi\u010di\u016bt\u0117, A. 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