Part 0 · 2 chapters · ~15 min

What a Platform Is

The economics of forks versus a shared core with adapters (the fork wins at country two and loses forever after the third), the itemised costs of each, how to make the decision at country two, and the inventory of what differs by country (money, identity, regulation, language, product shape) and what must not.

1

Product versus platform: the economics

the fork that looks cheaper
  1. Country two: a fork takes a month (copy, swap the currency and KYC, adjust copy); the core-and-adapter approach takes three (design the extension points, build the first adapter). The fork wins by two months, visibly, in a quarter where the launch date is real.
  2. Countries three and four: each fork is still a month, and every shared fix is now applied N times. An adapter against existing extension points is two weeks; the only growing cost is a new extension point when a country needs something unanticipated.
  3. The crossover between three and five: the forks have drifted, so a security fix is a week per fork; the design system is N migrations; there are N test suites, N pipelines, N on-calls. The fork's slope is N per change forever; the core's is flat.
  4. The fork's costs, itemised: every core fix, upgrade and design-system migration times N; N suites and on-calls; drift that makes the same bug different in each; features stranded in one country; and the migration back to a core, the most expensive project a platform team runs (part 6).
  5. The core's costs, itemised: extension points designed before the second country (part 5); a config system with a release process (part 2); a stricter core that cannot be hacked for one deadline; a platform team (part 7); the discipline to say no.
  6. The decision made well: at country two, name the five things that will differ, build extension points for those and nothing speculative, accept three months, and write down the fifth-country cost of the fork for whoever decides next. Made badly, it is the default: the fork, because it is cheaper this quarter.
THE FORK THAT LOOKS CHEAPER
cost per country over time: forks versus a shared core with adapters
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1/6
country two
Country one: one product; no decision needed. Country two: the fork takes a month (copy, swap currency and KYC, adjust copy); the core-and-adapter approach takes three (design the extension points: currency, identity, payments, tax, copy; build the first adapter). The fork wins by two months, visibly, in a quarter where the launch date matters.
2

What differs by country, and what must not

the inventory is the list of extension points
  1. Money: currency and exponent and formatting (the Trust course part 4), rounding rules, the payment rails with their clocks and failure modes (the Trust course part 3). An extension point per rail; the arithmetic is core.
  2. Identity: accepted documents, the KYC provider and its liveness method, tiers and what each allows (the Trust course part 2), screening lists. An adapter per provider behind one interface; the journey state machine is core.
  3. Regulation and tax: limits by tier and day, reporting thresholds, mandatory disclosures, retention, consent, tax on fees and interest; changing on the regulator's clock. A rules engine with country rule sets, authored by the country team, evaluated by the core (parts 2 and 4).
  4. Language and format: locale, script and direction, plurals (Arabic has six forms), calendars, date and number and address and phone formats, name order. Intl and message catalogues carry most; the layout must survive RTL and long strings (part 3).
  5. Product shape: features by licence, extra steps (a cooling period), different partners. The core defines flows with optional stages; the country config enables them; flags by geography (part 2).
  6. What must not differ: the ledger's semantics (the CBA module), the security model (the Trust course part 1), the design system (themed by tokens), the telemetry schema (with a country dimension), the release process (one train), the degraded states (the Trust course part 7). A country that overrides these is a fork with extra steps.
the exercise
List what differs between two countries your product serves, or would. Each item is an extension point with a cost; each thing you were tempted to put on the list that is really the same is a fork you avoided.
WHAT DIFFERS BY COUNTRY, AND WHAT MUST NOT
the inventory that decides the extension points
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money
Money: currency code and exponent (NGN 2, KES 2, JPY 0: the Trust course part 4), formatting (symbol position, separators), rounding rules for fees and tax, the payment rails (bank transfer rails, cards, mobile money, USSD) with their clocks and failure modes (the Trust course part 3). An extension point per rail; the money arithmetic itself is core.