The evolution of smart cities demands scalable, secure, and energy-efficient architectures for real-time data processing. With the number of IoT devices expected to exceed 40 billion by 2030, traditional cloud-based systems are increasingly constrained by bandwidth, latency, and energy limitations. This paper leverages the ROOF (Real-time Onsite Operations Facilitation) framework with decentralized computing at intermediary fog and peripheral edge network layers to reduce latency by processing data near its point of origin. ROOF features fog caching to avoid redundancy, ultra-low-power wireless transmission for energy savings, and AI-driven resource allocation for efficiency. Security is enhanced through TLS encryption, blockchain-based authentication, and edge-level access control. Case studies from Bhubaneswar, Barcelona and Copenhagen validate the use of ROOF in traffic systems and environmental monitoring. The paper concludes by outlining key challenges and prospects of AI-driven analytics in smart urban infrastructure.