so if a HTTP request comes in, how does it communicate with existing HTTP microservices and know that it's available or not? Does it do this by polling? I migh

so if a HTTP request comes in, how does it communicate with existing HTTP microservices and know that it's available or not? Does it do this by polling? I might actually give this a go since I need to route HTTP request to hundreds of flask servers but if they are busy, I don't want to keep hitting it.