SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79521bbce0e46817d7cc24479978e7d7830f28e0e8d61ebf35d40251768bee68' 
  AND token = 'c4MHSR1GZHzzzyqZVRCUmv9AsUkOXGp6iFXm87Ck/VQ=' 
  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