Appsync integration with AWS IOT is really inefficient and uneconomical

It is simply not economical to run millions of IOT updates through Appsync where active GraphQL users scan for the 0.00001% they are interested in. A much more efficient solution has been proposed in this form post:
https://forums.aws.amazon.com/thread.jspa?threadID=271817&tstart=0

Re: adding subscription resolvers for extended pubsub queries
With the flexibility of GraphQL directives, you could support other type of subscriptions, for example, something like:
type Subscription {
onMachineStateUpdate(id: ID): MachineState @aws_iot_subscribe(topic: [\"/MachineState/\\"])
}
Then a client could listen to IoT topics, through that subscription.

This scheme is very efficient since it leaves all of the IOT updates irrelevant to the active GraphQL users inside the IOT subsystem. When the GraphQL subscription starts, appsync would do the iot-subscribe and then tear it down when the user stops listening. MQTT messages from the IOT subscription would be applied as mutations. This is not something an external user can implement, the AppSync team needs to build this.

Read the issue description and the linked AWS forum proposal first; no repository file, test, or entry point is identified. Done would require an AppSync-supported subscription-resolver or directive design that routes selected AWS IoT topics to GraphQL subscribers, as described.

Written by the indexing model from the issue text.