# Real-Time Maintenance Optimization with Industrial Internet of Things
## 1 Introduction  
Maintenance is very important in manufacturing for many technical, financial, and safety reasons. First of all, it helps machines and equipment work reliably, so they do not break down suddenly and stop production. When machines work well, the production process is more stable and efficient. By doing regular maintenance, companies can make their machines last longer, which means they do not have to spend money on new ones too soon. This helps save money and makes it easier to plan for the future. Also, regular checks help find small problems early, before they turn into big, expensive ones. Well-maintained machines usually use less energy, which is better for the environment and lowers electricity bills. They also produce fewer faulty products, so there is less waste. From a safety point of view, maintenance helps prevent accidents and keeps workers safe. This is especially important when machines work under high pressure, heat, or speed. Following maintenance rules is also required by law in many places. If a company ignores this, it could be fined or lose important licenses or certificates. Another big advantage is that planned maintenance can reduce downtime, because it can be performed during quietperiods instead of during busy times. It also helps keep product quality high, since well-maintained machines are more accurate. Employees also feel better and more confident when they know the equipment they use is safe and reliable. In modern factories, predictive maintenance (using sensors and data) can make things even more efficient by warning when something might go wrong soon. Finally, good maintenance planning helps with managing spare parts, so companies always have what they need without overstocking. To sum up, maintenance helps factories work better, safer, and cheaper, while also keeping product quality high [1]. By using sensors to monitor the condition of system components in real time, companies can adjust their maintenance strategy instantly based on actual state information. This approach helps prevent unexpected failures and reduces unnecessary maintenance tasks. The paradigm of Industry 4.0 signifies a transformative shift in manufacturing through the integration of advanced digital technologies. Central to this concept are cyber-physical systems, the Internet of Things (IoT), and big data analytics, which collectively enable real-time monitoring, control, and optimization of industrial processes. Smart factories exemplify this evolution, where interconnected machines and systems operate with high levels of autonomy and intelligence. This paradigm facilitates mass customization, operational efficiency, and enhanced responsiveness to market demands. Moreover, Industry 4.0 supports sustainability objectives by promoting resource efficiency, predictive maintenance, and reduced environmental impact. Thanks to Industry 4.0 technologies and the Industrial Internet of Things (IIoT), it is now possible to collect and analyze data continuously. As a result, maintenance becomes more efficient, cost-effective, and better aligned with the real needs of the production system. In this article, the authors examine how the application of IIoT technologies can improve the efficiency of maintenance operations in a production system. This research aims to offer valuable insights into real-time maintenance strategy optimization, where real-time state information supports the cost-effective and reliable maintenance. The first part of the article provides a comprehensive literature review, offering an overview of the current state of research in the field of maintenance optimization, focusing on the application of Industry 4.0 technologies, including IIoT solutions. It highlights significant findings, identifies key challenges, and uncovers research gaps that need to be addressed. Section 3 describes the model framework of both the conventional and IIoT-supported maintenance strategy optimization.