In one embodiment, a network assurance service receives a first set of telemetry data captured in a first network monitored by the network assurance service. The network assurance service computes, for each of a plurality of other networks monitored by the service, a similarity score between the first set of telemetry data and a set of telemetry data captured in that other network. The service selects a machine learning-based anomaly detector trained using a particular one of the sets of telemetry data captured in one of the plurality of other networks, based on the computed similarity score between the first set of telemetry data and the particular set of telemetry data captured in one of the plurality of other networks. The service uses the selected anomaly detector to assess telemetry data from the first network, until the service has received a threshold amount of telemetry data for the first network.