Our client is using pega 7.1.9 with pega marketing 7.13 and planning to upgrade pega 7.3.1 and PM 7.31.
Main concern from business is that they can't have downtime more than 4 hours.
For pega platform upgrade - we can follow 2 database approach to minimize the downtime.
For PM upgrade - As PM 7.13 is not compatible with pega 7.3.1, none of business flows are working. we need to wait for PM 7.31 to make it work. We estimated PM upgrade in low environment and it takes 2 days appx (upgrade to 7.22 first then 7.31).
But client is not convinced with this upgrade process in 2 days(PM upgrade)