The increasing softwarisation of mobile core network functions is fostering the evolution of the mobile network architecture itself, which in its fifth gen- eration (5G) has moved towards a service provider/consumer framework and service-based interfaces. Moreover, the 5G architecture is suitable for the exploitation of the mobile technology for dedicated, non-public uses as an alternative to nation-wide deployments. The 5G core networks are a crucial part of this architectural paradigm shift, which aims at closing the gap be- tween the telecommunications domain and the information technology world at large. The objective of this article is to discuss the adoption of software design concepts like microservices and cloud-nativeness in the context of mo- bile networks. Specifically, we will i) advocate the need for a non-trivial adaptation of the 5G core network and a redesign of its functions into a microservice-based architecture, ii) identify an approach to achieve this ob- jective and put it into practice by decomposing three exemplary network functions, both theoretically and practically, in microservices in charge of distinct responsibilities, and iii) propose ways forward towards the adoption and further extension of these concepts in beyond-5G mobile systems.