Smart cities rely on torrents of sensor, device, and citizen data to optimize transport, energy, safety, health and other urban services. Converting that raw stream into actionable insight hinges on data engineering. This paper surveys global smart‑city domains and maps their technical demands—IoT networks, edge‑to‑cloud pipelines, big‑data platforms, and real‑time stream engines. We trace the full data lifecycle (collection to visualisation) and show how data engineers design scalable, quality‑controlled, and secure pipelines while enforcing privacy and ethical‑AI safeguards. Case studies from Barcelona, New York, and other cities demonstrate tangible gains—lower energy use, faster emergency response, improved transparency—achieved through well‑architected data systems. We conclude that robust, interoperable data‑engineering practices are the decisive factor in realising safe, sustainable, AI‑driven smart‑city services.
Keywords: data engineering, iot analytics, real‑time big data systems, smart cities, urban data infrastructure
