REDIS_SPAN_ERROR_RATE: float [0, 1], Percentage of redis spans that will be flagged as an error
EXTERNAL_DB_NAME: string, Name of external database
EXTERNAL_DB_ACCESS_RATE: float [0, 1], Percentage of redis spans that will be turned into external database spans
EXTERNAL_DB_MAX_DURATION_MILLIS: int, Artificial delay added to external database spans (mock value)