SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b542e75b82ae49353c57537f824c1773ff648291cd75d290858039c5563c73e' 
  AND token = '78VZardH1hVXpfd5C5ZRwbrZrz5uNH56Sx+/IlZvSuI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

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