A processor-implemented method includes receiving machine learning model updates from clients in a federated learning system. The method also includes determining a fixed local zone associated with each of the clients, the fixed local zone having a first fixed boundary. The method includes updating model weights of a central machine learning model based on local machine learning updates for a local subset of the clients corresponding to the fixed local zone. The method includes updating the model weights of the central machine learning model based on neighbor machine learning updates for a neighbor subset of the clients. The neighbor subset corresponds to a fixed neighbor zone that neighbors the fixed local zone and has a second fixed boundary. The neighbor machine learning updates have a different weight than the local machine learning updates when updating model weights. A value of the different weight corresponds to a similarity parameter.