SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28e840be2df9461960c90fc0e84a4587278f422c5a76014aff832d0444f97e18' 
  AND token = 'jZn4D0bXPqCoJduXNiKq8KP1tAV5/NVwMqaRXd2arMo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

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