This. Even though you/we are [mostly] focusing on the tech aspect of the world, make no mistake; the “business side” (or the political) can kill your migration project more suddenly and decidedly than you can spell ‘strangler pattern’.

So, to add to the comment above:

- does your migration affect the clients and the way clients work in any way? No matter how small, if the answer is “yes” then you need to ensure full buy-in from the clients. Even if your migration went flawlessly from a technical perspective, if a large enough client didn’t realise that V2 comes with some change that he doesn’t like, and when the change hits him after the migration, he raises this as a problem and escalates the problem high enough up the food chain with the message “this is not working for us” then you are going to be rolling back, regardless of the technical stuff. So, realise that the clients are big stakeholders and they need to be managed from the beginning of the project until some time after your V2 go live. In my experience the best results come from bringing them close to the project early and get some buy in by having them e.g. do some end-to-end testing if V2 and get them to accept the V2 before the go live. Preferably in an email for if things get ugly at some point (it happens, is sucks).

- also as the comment above says, don’t ignore the political. You should know what every important stakeholder gets out of this? Don’t forget personal ambition, ego, promotions etc as possible motivators for stakeholders. Who of the stakeholders are supporting your project now, and who is not? And just as important, what may change for a stakeholder to “switch camp” from supporter to not. Maybe the stakeholder is a mid-level manager who is measured on some KPI and V2 will make his KPI look better. So he’s a supporter. But then his company gets a new ceo and the KPIs change. Now he is no longer a supporter because V2 doesn’t give him anything he wants. And he’s actually now against your project because he has to commit some resources to it, but doesn’t get anything, so actually if your project is killed he frees up resources and doesn’t loose anything.

From one developer to another; The tech part is the easier part I’m sorry to say.

I guess I need to clarify what I mean by the psychological component.

Technical and political components are external. Career aspirations and mitigating boredom/stagnation by pursuing complicated work create motivations to invent interesting projects.

And there’s the ability to claim integration from v1 to v2 as progress. Rather than only change.

To put it another way there is always some degree of change for the sake of change motivating our desires for change. Particularly when a big chunk of our time must be accounted for. Typically, playing video games, sleeping, and walking a dog through the woods instead are not viable alternatives in contexts where data migrations are being considered.

If migration was something the OP didn’t want to do, the question would be about finding a new job.