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Crypto Checkout Infrastructure for Multi-Tenant Shops

Non-custodial XMR and WOW checkout, plus Grin via BTCPayServer

Our multi-tenant webshops run on MedusaJS with a BTCPay plugin for Bitcoin and Lightning. We wanted to add privacy coins: Monero, Wownero, and Grin.

BTCPayServer does have a built-in Monero plugin, but it is custodial (a single server-side wallet receives all payments) and only supports one wallet per instance. That does not work for multi-tenant shops where each merchant needs payments sent directly to their own wallet. So we forked xmrcheckout, an existing non-custodial checkout, and built from there.

XMR Checkout

xmrcheckout is self-hosted and non-custodial. Each merchant provides their primary address and secret view key. The system uses view-only access to derive unique subaddresses per invoice and detect payments. It never holds spend keys or moves funds.

Stack: Python/FastAPI backend, Next.js frontend, wallet-rpc for chain queries, Postgres for state, all in Docker Compose. XMR/USD rates from the Kraken public API.

Hosted at xmrcheckout.such.software.

WOW Checkout

wowcheckout is a fork of xmrcheckout for Wownero. File and folder structure is identical to upstream so merging fixes stays easy. The content-only differences:

  • Network bytes — Wownero address prefixes (53, 63, 54), patched at runtime
  • Pricing — WOW-BTC from Nonlogs multiplied by BTC/USD from Kraken (no direct WOW/USD pair exists)
  • Daemon — Wownero node, binaries from Codeberg

Hosted at wowcheckout.such.software.

Grin via BTCPayServer

Grin's transaction protocol is interactive — sender and receiver exchange slates to build a transaction. The checkout system must hold a wallet with spend authority, making it semi-custodial by nature.

We contributed a Grin plugin for BTCPayServer that talks to grin-wallet's Owner API to issue invoices, finalize transactions, and track confirmations. It slots in alongside Bitcoin and Lightning with no extra Medusa integration work.

Trust Model

  • XMR and WOW — Fully non-custodial. View-only access. Funds go directly to the merchant wallet.
  • Grin — Semi-custodial. The server holds a Grin wallet with spend authority because the protocol requires it. Merchants trust the operator to forward funds. This is inherent to Grin, not a design choice.

Medusa Integration

MedusaJS already has a BTCPay payment plugin that handles invoices and webhook callbacks. Because xmrcheckout and wowcheckout expose a BTCPay-compatible API, the same plugin works for all currencies with just a base URL change. One integration pattern for BTC, Lightning, XMR, WOW, and GRIN.

Source

Work With Us

If you want a managed webshop that accepts cryptocurrency — BTC, Lightning, XMR, WOW, GRIN, or a combination — we can set that up for you. Get in touch.