This is a good example of the kind of case study I will point to when someone starts to get cranky with my unyielding principle of putting the
entire business inside a single SQL database.
When you have geo replicas and point-in-time restoration capabilities which can synchronously bring 100% of the business back from the dead in a matter of seconds/minutes...
How many $8.4m days before a complete rewrite of all systems would be justified? If you are going to entertain a rewrite, why not use one system to rule them all so you can audit one thing and move on with life?
This industry does not seem like a good fit for non-traditional technology stacks. I'd strongly consider putting my entire casino on a mainframe if I could. Any vendor who indicates a lack of willingness for integration with that tech stack would be instantly disqualified from selection. I feel like this is a really good technology bullshit filter for the kind of industry MGM is operating in. If it's not good enough for Visa or Amex, it's not good enough for a gambling operation.