src/RunOpenCode/ExchangeRate/Repository/DoctrineDbalRepository.php
protected function getRateKey($currencyCode, $date, $rateType, $sourceName)
    {
        return str_replace(
            ['%currency_code%', '%date%', '%rate_type%', '%source_name%'],
            [$currencyCode, $date->format('Y-m-d'), $rateType, $sourceName],
            '%currency_code%_%date%_%rate_type%_%source_name%'
        );
    }
protected function getRateKey($currencyCode, $date, $rateType, $sourceName)
    {
        return str_replace(
            ['%currency_code%', '%date%', '%rate_type%', '%source_name%'],
            [$currencyCode, $date->format('Y-m-d'), $rateType, $sourceName],
            '%currency_code%_%date%_%rate_type%_%source_name%'
        );
    }
Builds rate key to speed up search.

@param string    $currencyCode
@param \DateTime $date
@param string    $rateType
@param string    $sourceName

@return string