SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '538e81944f4d831b9f52a636c0fe2cfd84a2616a50dbaa5918bbd6d353969692' 
  AND token = 'Fp6TFZiWsP7AxzQeHUxWLKMrdTAsNrn4saQv1/U/A9k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE Impossible WHERE noticed after reading const tables