That depends entirely on the status of the stack when the code freeze happened.

If it was unstable, then I'd want several bottles of whisky on hand, because I'd have to work around the stinky pile of dung I'd been left with.

Given reports of debug and dev builds in production just before everything was frozen, I'd probably want to start stocking up on whisky.

Changes to a system can come in many ways, e.g. we had a noticeable increase in our db size because of a new customer data, what was ok. before wasn't after. Of course it's different for twitter. And what about security? Update to libraries, dependencies...?

Anyone remember the leap second?

Of course but this is also twitter, not a startup in its infancy. I'm not saying new stuff won't happen (etc), but they have a very mature infra org.

Do they? It's hard to tell where these cuts are happening and how much thought is going into them.

And almost no one left to manage it.