Is there a way to configure some of the envoy cluster parameters for the PassthroughCluster such as max_connections (https://www.envoyproxy.io/docs/envoy/latest/api-v2/api/v2/cluster/circuit_breaker.proto#envoy-api-field-cluster-circuitbreakers-thresholds-max-connections) For other in-mesh clusters DestinationRules can be used to specify that value.
With traffic policy set to ALLOW_ANY, mesh-external calls will all go through the PassthroughCluster. Currently it seems like this value is not set explicitly, in which case the default of 1024 connections will apply, which may be impractical for some applications.