SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a4731be6d7ab6c4c6a90399d353fbd0d5429a4e778228a61adf7b1b3581c259' 
  AND token = 'xcrVTbxoKZ1/pjhGZClwNcc+Iyc+x0Xs4FBkIg2wzgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

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