SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c878039b338796863efee98abdcaefc25a29a9c8d9f718589930cf3241c345ad' 
  AND token = 'Z2LhtqB3PJiA9lpky/or6BqPMyRQo3NfmOOl48T0ob4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

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