Short write‑ups of problems we hit running a real commerce operation and what we changed in the code because of them. No product announcements; just the reasoning.
Selling through a wholesale marketplace means the order is not yours: the buyer edits it after you have picked it, the marketplace sets the discount and the commission, the items can change after dispatch, and the only truth is their payload. The shops we run on such a marketplace taught us more about ownership than any other integration — six rules, each with the afternoon behind it.
We did not rewrite the twenty‑year‑old system and flip a switch. We built the new one beside it, pulled the data across entity by entity with 106 fetchers, ran both for years, and moved one company at a time — 588,000 customers, 1.08 million invoices, eventually 88 million rows of history. The "source id" on every row, the fetchers that could not be allowed to overwrite what people had edited in the new system, the guard that froze the catalogue, the import of two decades of audit trail, and the rule that a closed shop must rest in peace.