I don't know what he refers to. But there is a specific kind of zero downtime deployments which can restart without losing in-memory state, like Erlang. Erlang

I don't know what he refers to. But there is a specific kind of zero downtime deployments which can restart without losing in-memory state, like Erlang. Erlang also provides "fix in minutes, in production" stories he refers. For most of languages, it's very hard to remotely get access to an object, let alone fix things directly. With Erlang, you can inspect every object in the cluster to understand what's going on for any user, and fix the plane in the mid-air instead of rebuilding a plane with the same issue, then go through the process to fix it.