The MEC paradigm calls for a distribution of computational capacity at the network’s edges. While MEC will play a key role in future 5G deployments, it will take some time until the existing 4G networks evolve into a full 5G system. A challenge exists to devise a transition mechanism that allows MEC features to be seamlessly integrated in the current 4G networks. This article introduces a lightweight, ETSI-compliant MEC solution for 4G and 5G networks. The proposed solution, which we name LightEdge, has the main goal of immediately making available the features and capabilities of edge clouds to mobile users. This article reports on the design and implementation of LightEdge and on its evaluation in a practical latency-sensitive use case.