[mikepurvis]

I would say more significantly, 4 million people can read it. The changes required for any given quarter are probably miniscule, but the tricky part is getting up to speed on all those legacy patterns and architectural decisions.

A model being able to ingest the whole codebase (maybe even its VCS history!) and take you through it is almost certainly the most valuable part of all.

Not to mention the inevitable "now one-shot port that bad boy to rust" discussion.

[happycube]

You also need "make no mistakes"

[Jare]

Run both systems side by side for 9 months. Banks have patience.