Smart Mutation Processing for Subscriptions

Hi.
I have a use-case where new objects, that added to Dynamo Db are published over AppSync real-time subscription channel. Due to specific usage pattern (large volume of writes as compared to number of active listeners that subscribed to filtered output) most of the time I don't need to publish those mutations, since nobody listens for them. I want to optimize mutation resolver lambda to work only if at least one active listener is present. Is there any API to check whether given mqtt topic has active subscribers, or configuration, that allows me to make mutation lambda working on active topics only?