SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '314cd0b5e9ffba7b56e33f93a7b370040981dd0fb840d7b437ace50215992419' 
  AND token = '391p919kWMrnv2eTANR4wPi1vKlWvq+qyNL4JIKEcac=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}