Share

A trustworthy number still has to survive crossing a boundary - another team, another legal entity, another country, another system that consumes it automatically. Most of the time, it doesn't. It arrives as an export, gets copied, and quietly goes stale the moment nobody's watching it anymore.

Share is the third guide in THE FOUR MOVES series: how to build a shared number as a genuine product - with an interface, a named owner, a published promise, and a real consumer - rather than a one-time file handoff. It draws directly on data mesh (Zhamak Dehghani) and Google's Site Reliability Engineering discipline, credited by name, and works through the real legal terrain most guides skip: GDPR's purpose-limitation and cross-border transfer rules, and Sweden's co-determination law, both explained precisely rather than approximately.

• The four requirements that separate "shared as a product" from "exported as a favor"
• A tiered access system for saying yes by default, safely, without individual negotiation every time
• Who owns a shared number at 3am when it breaks - and why that has to be a named person, not a team

Read after Curate, or on its own if your numbers are trusted in isolated pockets that don't yet talk to each other, or to the systems that increasingly need to.