[osigurdson]

I'd argue for Option 3, which is to try to understand the workloads placed on the original system and then design the new system based on this. I think having 2K independent database servers would not normally be optimal for 2M users, but it is possible.

[hedora]

If the old system is exceeding uptime SLAs, meeting all business needs, and coming in under the budget for such an investigation (it sounds like the total operations budget was less than 10% of one engineer's time), then why bother?

[osigurdson]

I don’t know the situation, not touching it may have been optimal. I’m suggesting that if it was going to get re-written, I would at least study the basic parameters of the problem by reviewing the workload of the current system.