## 1 Introduction
It is generally commonplace to assert that the Internet of Things (IoT) allows humans and computer systems to interact with billions of devices or data collection IoT appliances, such as sensors, actuators, services, and other gadgets that are featured with an Internet connection, or another kind of data interface. It is immediately noted that IoT devices are placed between cyber and physical environments, which significantly improves the general human capacity to interact with the environment. From this point of view, the research IoT approach could face cybersecurity problems by harnessing the properties of its own devices and information and communication technologies (ICTs) [6] or could consistently benefit from artificial intelligence support for efficient solutions [7,8]. Middleware systems or software layers, which are commonly defined as a software system designed to intermediate the link between IoT devices and related applications, represent a fundamental technology. Therefore, the proposed IoT middleware architectures must comply with the requirements of the related IoT ecosystem to be adopted as a proper solution on a larger scale. The service-oriented architecture (SOA) represents one of the approaches that is particularly considered. In this context, the particular type of service-oriented paradigm, which is represented by microservices, has naturally built a hype in the realm of cloud and enterprise-oriented applications. Moreover, the microservices model is particularly  
Figure 1: Multilayered architecture for shared data service. convenient relative to dynamic IoT applications, which usually consider architectures that are based on the usage of microservices. The contribution that is reported in paper [9] represents an overview regarding the practice and use of IoT microservices architectures. Thus, the authors assess the requirements of a typical IoT middleware through an investigation that addresses the requirements for the design and implementation of the appropriate middleware architectures. Additionally, the interested reader may consult the rather extensive review concerning the broader scope of microservices architectures security, which is presented by the authors of [10; 11]. The contribution that is described in this paper considers microservices as basic pillars of the respective system's architecture, which is concerned with the efficient and secure management of tens of thousands of electricity meters. The microservices use standard TCP data channels in order to exchange data between them and also with other system components. Nevertheless, for the TCP-based traffic, some use-case scenarios require to be translated to DNP3-based data traffic [12], which is compatible with the specific Supervisory Control and Data Acquisition (SCADA) architectural components of the system. In Section 2.2, some of the most relevant existing contributions are analytically enumerated. The rest of the paper is structured according to the following sections. Significant existing papers are presented in Section 2.1, which also pertain to the scope of understanding the supervisory control and data acquisition systems (SCADA) described in Section 2.2. Furthermore, the shared data microservice is thoroughly described in Section 3, from an architectural and implementational perspective. Moreover, the authentication microservice (see Section 4) is also presented and evaluated. In the next Section 5, further security aspects for the energy platform related to the microservices that consider IoT devices are presented and analysed. Consequently, the real-world significance of the approach that this paper proposes is evaluated and discussed. The last section concludes the paper.