Solidus
Solidus is the app that makes physical gold usable every day: a personal account with an Italian IBAN, a Mastercard debit card and 999.9 gold that you can buy, accumulate, spend or have delivered home, all from your phone.
About this project
Who is Solidus?
Carrara S.p.A. has been melting, refining, assaying and trading industrial and investment gold for more than 50 years, and is registered with the Italian OAM as a professional gold operator (no. OPO402). With Solidus it took that expertise to retail savers. The idea is simple: an account whose balance is physical gold, certified by Carrara and kept in a high-security vault, next to a euro wallet for everyday spending. Solidus has been covered by Il Sole 24 Ore and Milano Finanza.
What did Solidus need?
Gold and e-money live in two different worlds. Treezor, the e-money institution that issues the Solidus account and card, handles euros; it cannot hold a gram of metal. Solidus needed both to work as one product. A user buys gold in grams at the live price, then pays at a checkout with a Mastercard card. If the euro balance falls short, the missing amount has to come from selling exactly the gold needed, in real time, while the card authorisation is still open. Around that core sat the usual weight of a regulated consumer product: full KYC with a gold custody contract signed during onboarding, plan-based pricing, payout controls, invoicing, customer care, and the reporting owed to the Bank of Italy and the Italian Revenue Agency, which could not depend on someone exporting spreadsheets by hand.
What did GrowishPay deliver?
GrowishPay built proprietary gold wallets next to the Treezor euro account and one backend that turns them into a single balance. The same API serves the iOS and Android app, the web app, the back office and the online shop, which is integrated with StoneX Bullion’s wholesale service. Invoices and the reports to the Bank of Italy and the Italian Revenue Agency are generated automatically. GrowishPay is Solidus’ Master Tech Partner: architecture, development, integrations, QA and day-to-day operations.
live with real customers
gold and euros in a single view
gold sold while the card payment is authorised
Bank of Italy and Revenue Agency filings generated automatically
How paying with your gold works
Buy gold in grams
The user buys grams at the live price from the euro balance, starting from 2 g, or builds them up over time with a recurring plan.
Switch on pay in gold
In the card settings, one toggle lets the card draw on gold whenever the euro balance is not enough.
Pay anywhere
The user pays in store or online with the virtual card from day one, or with the physical Mastercard.
Instant sale at checkout
If the euro balance falls short, the platform sells exactly the grams needed at the live price while the card authorisation is still open.
The rest stays gold
Only the missing amount is converted. The remaining grams stay in the wallet, ready to be sold, spent or delivered home as bars.
With PAR, the recurring purchase plan, the user picks a fixed number of grams (2 g or multiples of 2) and a frequency, and the app buys the gold on every due date from the euro balance, in a separate wallet and with no lock-in.
In our technical solution, we used:
Treezor is the European e-money institution, supervised by the French ACPR, that issues the Solidus euro account with Italian IBAN and the Mastercard debit cards. GrowishPay integrates its APIs for KYC, accounts, cards and SEPA transfers.
Amazon Web Services runs the whole platform on ECS and Fargate, defined as infrastructure-as-code with Terraform, with WAF protection and progressive releases via CodeDeploy.
React and Next.js power the customer web app, the back office and the online shop, on the same API as the mobile app.
Node.js and MongoDB run the core backend that manages gold wallets, live pricing, plans, recurring purchases and the link between gold and euros.
Salesforce handles CRM and customer service, kept in sync with the platform’s user and transaction data.
GrowishPay OrchestrationCore Suite: our modular platform for Treezor-based solutions. OrchestrationCore orchestrates transactions and flows, PricingCore manages plans, fees and business rules, SentinelCore monitors transactions in real time, GrowthCore runs referral and incentive programmes, ComplianceCore keeps the audit trail and compliance reports, and AICore lets teams ask their data in plain language.
Let’s embed finance together!
Let us know your ideas and needs and we will be in touch shortly