About the USD to BRL rate
Brazil has at times maintained some of the highest interest rates among major economies to control inflation, which has made the real attractive to certain carry-trade strategies but also exposed it to sharp moves when global risk sentiment shifts.
USD/BRL is closely watched around Brazilian central bank (Banco Central do Brasil) interest rate decisions, since rate changes there can swing capital flows quickly given how much higher Brazilian yields have often been than US ones.
For anyone doing business with Brazil's large agricultural or manufacturing export sectors, or planning travel there, this rate has historically moved enough over a single year that checking it close to the time of a transaction matters more than for steadier pairs.