Not answering the question, but k8s doesn't entirely solve this because of the DB. If you're a SaaS provider that reached this scale, there's a good chance your architecture isn't just stuffing everything in one Postgres instance, so shipping a VM with Mongo, Postgres, Zookeeper, and Cassandra sorta makes sense.
If you'd had ample foresight, it might have been nice to have an architecture where the DB is truly abstracted away. Or not. Maintaining two backend implementations is a pain and error-prone.
If you'd had ample foresight, it might have been nice to have an architecture where the DB is truly abstracted away. Or not. Maintaining two backend implementations is a pain and error-prone.