The Global Payment Platform in a JSON File
Work from the brief alone. Write what you would produce — actors, requirements, data, a first slice, your unknowns — before opening anything below it; the exercise stops working if you read the reality first.
A colleague proposes that the company's new global payment platform — many currencies, several providers, merchants in many countries — store all transactions in a single JSON file on the application server, "to keep it simple until we need more". Identify the requirements that make this insufficient, and say which of them are requirements and which are your assumptions.
Your attempt
Nothing here is checked. It exists so that the reveal below is a comparison rather than a reading.
Answering with the opposite extreme — a multi-region, event-sourced, sharded ledger with a Kafka backbone — because the JSON file was obviously wrong. It replaces a design with no requirements with a design with imagined ones, and neither can say which requirement each component serves; the exercise was to derive the requirements, and both answers skipped it.
Read this even if you are confident. It is here rather than behind a button because it is the move most people actually make, it produces things that look like a project, and its cost arrives when the first hard requirement has nowhere to go.