SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6d707c3fa0a1dcb5dd2cece68e3e4598537d55557522576e48a675ddaacb1ce' 
  AND token = 'uPfXWfQ6tZ5WHXNiid9tBeZ2aRr1QY+0i226MU9s1SE=' 
  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