We have a distinction between aggregated data types and raw data types. OHLCV and Exchange Rates are aggregated, so we need to have some time period in which aggregation is happening.
All aggregated data types we have start from 1 SEC interval. If the data type/data stream is not aggregated then we are operating in real-time, disseminating all updates and providing data access in the historical API and flat files (aka tick by tick) through our other website, Cryptotick.com.
To see the time periods you can use for Exchange Rates and OHLCV data, please see here: https://support.coinapi.io/hc/en-us/articles/8932700219549-What-are-the-time-periods-I-can-use-for-Exchange-Rates-and-OHLCV-