Hi @Kevin_Cantrell and welcome in the MongoDB Community :muscle !
It’s impossible and (I’m pretty sure) will never happen.
MongoDB Atlas provides MongoDB clusters as a service. You can’t alter the configuration or adds nodes in it without using the Atlas UI (or API) and definitely not external nodes that wouldn’t be under the control of Atlas. This defeats the entire purpose of being “as a Service”.
Everything is automated in Atlas.
- How would your node be upgraded automatically?
- How would Atlas performs the security updates on the OS?
- How would Atlas be able to monitor the hardware? If you scale up from M30 to M50, how can Atlas add more computation power on this external machine?
- How would the network security be enforced if an external machine add access to the internal Security Group?
It generated way more problems that it solves. So to sum up. Not happening.
It will be a lot safer for you to have the Primary managed by Atlas as well in Atlas and identical to the 2 other nodes, monitored, secured, backed up, automated, etc.
Cheers,
Maxime.