A cloud migration is rarely an infrastructure problem. It is a sequencing problem with a network topology attached. Move the wrong thing first and you spend the rest of the project working around a decision you cannot undo without starting over.
Most sessions that start with "the container can't reach the database" end at one of four or five misunderstandings. Docker networking is not magic — it is Linux bridges, veth pairs and iptables with a convenient API on top. Once you can see those three things directly, the guessing stops.
Ingress controllers got most of us started, and Ingress is not deprecated. But on a multi-tenant platform it fails in a specific, predictable way: one object ends up owning TLS, routing and rate limits, which means three teams edit the same YAML and none of them owns it.