Nerve

Two applications that ship together: a Next.js control panel for subscriptions, licence issuance and multi-tenant administration, and an Electron point-of-sale terminal that runs on the shop floor. The hard part was not the CRUD - it was making a licence genuinely unborrable. Keys are signed with RS256, only the hash is stored, and each terminal is bound to a hardware fingerprint derived from the CPU, the motherboard and the MAC address. Copy the database to another machine and the token fails to verify, because the claim in the token no longer matches the machine asking. A kill switch with an anti-tamper HMAC and a clock-rollback guard sits underneath it all, and the whole thing has to survive a 12-year-old jQuery admin panel being replaced in one go.