You can scale firecracker vms like really fast. In our shop we have a simple go service that maintain the state in a sqlite database. The only requirement is bare-metal servers.

I'm a huge scheduling nerd, and the container scheduling system in this post is probably the most impactful system I've worked on. It's quite different than existing solutions, and I personally feel it's at an interesting point in the design space -- very distributed, no strong consistency anywhere, and oriented towards massive scales. Would love to hear feedback and thoughts!