The edge or edge computing refers to the computational infrastructure between sensors and Internet-of-Things world on the one side and centralised cloud data centres on the other. Edge clusters could consist of small single-board devices, which are widely used in different applications. This includes microcontrollers regulating an industrial process or controllers monitoring and managing traffic roadside. Although generally hardware capabilities of devices are growing, resources at the edge are often still limited, requiring an intelligent resource management. This can done through self-adaptive scaling mechanisms in these clusters allowing to scale components of the application in the cluster. We introduce here an auto-scalable cluster architecture for lightweight container-based edge devices. A serverless architecture forms the core of this architecture. The auto-scaling component is based on fuzzy logic in order to better manage uncertainty problems arising in such contexts. Our evaluations show that our platform architecture and the auto-scaling functionality satisfy the need of lightweightness in edge architecture.