I started with the UX layer and currency defaulting logic, which felt safe, but the interviewer kept pushing on the storage side.
Start by clarifying requirements and scope, then propose a high-level architecture that separates currency selection, conversion, and pricing logic. Dive into data modeling for storing prices in multiple currencies, handling rounding and taxes, and ensuring consistency in refunds. Discuss trade-offs and potential edge cases.
Pro tip: Emphasize the importance of storing prices in the base currency and converting at display time to avoid inconsistencies, but also mention the need for caching exchange rates and handling rate fluctuations. Show awareness of regulatory and tax implications across regions.
Ask questions to understand the scale, supported currencies, and specific business rules (e.g., rounding policies, tax handling). Confirm whether prices are set in a base currency or per currency.
Outline how users select a currency (e.g., based on locale, user preference, or manual selection) and how conversion rates are fetched, cached, and applied. Discuss using a service for exchange rates and handling rate updates.
Propose a schema that stores prices in a base currency (e.g., USD) and optionally in local currencies for performance. Explain how to handle rounding rules and ensure consistency across services.
Describe how taxes are calculated per region and currency, and how refunds are processed using the original exchange rate or current rate, with clear policies. Ensure idempotency and auditability.
Discuss strategies like using a single source of truth for pricing, caching exchange rates, and handling edge cases (e.g., currency fluctuations, rounding errors). Mention monitoring and fallback mechanisms.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.