Loop 02 · Substrate
Developers D1

Developers

Issue your first card in one call.

A sandbox with test BINs from day one, idempotent endpoints, and a webhook for every ledger event. Everything the production system does, the sandbox does with test money.

Get a sandbox key →API reference
curl sandbox.qbfintech.com
# create a virtual card with a category rule
curl -X POST /v1/cards \
  -H "Authorization: Bearer sk_test_…" \
  -H "Idempotency-Key: 7c1e…" \
  -d '{"holder_id":"usr_8f2c41","type":"virtual",
       "currency":"USD","limit":250000,
       "controls":{"mcc_allow":["5734"]}}'
201 card_2f91be · active

Endpoints

Four resources. Everything else hangs off them.

POST/v1/accountsOpen a named multi-currency account for a holder
GET/v1/accounts/{id}/balancesBalances by currency, available and pending
POST/v1/cardsIssue a virtual or physical card with controls preset
POST/v1/cards/{id}/freezeFreeze instantly; unfreeze is the same call
POST/v1/payoutsSend on the domestic rail for the corridor, or on-chain
GET/v1/ledger/eventsEvery posting, in order, with the webhook id that announced it
POST/v1/webhooksSubscribe to card, payout, ledger and holder events

Go live

From sandbox key to production in four steps.

Step 01

Build in the sandbox

Day 1

Same endpoints, test BINs, simulated authorizations and settlements. Break things here.

Step 02

Programme design

Week 1

Products, markets, card artwork, commercial structure. We tell you what is available for your model before you commit engineering time.

Step 03

Compliance review

Week 1 to 2

Your business, your downstream clients, your onboarding flow. The licensed partner makes the final call; we tell you the reason if the answer is no.

Step 04

Production keys

Day 142

Swap the key. Nothing else changes.