It’s unacceptable in any form.

5 tons you say?

Versioning is one way; if you have an API you can have different versions which will can change depending on version.

E.G. let’s say you have contact information coming through an API… the database can largely remain the same, but if you want to add a field or change a fields name, you could upgrade the version. When the app is ready to use the new version, switch the app over.

Rereading your question once more, I believe you can just resolve all your issues with a common API.

You mean vine?

Excellent! CDN and DDoS protection are essential. Also would recommend looking into load balancing if you haven’t.