Pick a depth. Each prompt opens in your AI pre-loaded with the lesson. Click a row to preview the prompt.
If your product touches multiple currencies, every transaction requires a foreign-exchange decision: which rate, with what spread, when locked, who bears the rate risk. The naive approach (live mid-market rates at conversion time) costs the business 50-150 bps per transaction. Doing it right is one of the highest-leverage product-engineering investments.
FX mechanics and rate sourcing.
Components of an FX transaction:
1. Mid-market rate: the theoretical "true" rate (Reuters, ECB, central bank)
2. Spread: markup added by your FX provider (typically 25-200 bps)
3. Service fee: flat or % charged to the customer
4. Settlement timing: rate-lock window before settlement occurs
Common patterns:
PATTERN A: Real-time conversion
- User pays in USD; merchant receives in EUR
- Locked at the rate at moment of transaction
- User absorbs FX cost; merchant gets EUR net of spread
PATTERN B: Held in customer's currency
- User has a USD balance; spends in EUR
- Each spend converts at moment of spend (rate locked then)
- Customer makes spending-time FX decision
PATTERN C: Multi-currency wallet
- User holds balances in USD, EUR, GBP simultaneously
- Funds transferred between wallets at user-initiated rate
- Lowest FX cost; highest operational complexity
Rate sources (B2B):
Reuters/Refinitiv: institutional quality, expensive ($10k+/mo)
ECB reference rates: daily fix; free for non-commercial use
Open Exchange Rates / Fixer: low-cost APIs, ~5-minute refresh, $50/mo+
Currencylayer / Wise: low spread quotes, sometimes API access
Compliance:
Settlement rate disclosure required in EU (PSD2) and some other jurisdictions
"True cost of FX" must be displayed to consumer
Real-world spreads (mid-2026):
Wise (Transferwise): 25-50 bps + flat fee
Revolut Premium: flat fee, 0 bps weekday market hours
Banks: 150-350 bps + flat fee
Crypto on-ramps: 50-200 bps