SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50c191395ac0525ca3ecf2e27a8c5ab6f3a71155dd5079f54436d7606bbefcd9' 
  AND token = '6l08IPIU9zv1IyDRcT+EDzjZ74bZG3sC5SeRP70/I+k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

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