ETF API Data Quality Checklist for Production Apps

A metadata universe and a priced universe are not always identical. Count how many active ETFs have at least one historical observation and ensure your UI distinguishes unsupported or unpriced symbols.

Check uniqueness by symbol and date, positive price values, OHLC consistency, chronological ordering, and the latest available trading day. Investigate large gaps instead of automatically filling them.

Test authentication failures, rate limits, invalid symbols, insufficient history, timeouts, and stale caches. Production readiness includes observable errors and freshness—not only successful responses.