SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4253424af8749f97fedc7eb01e49eec6d222e36f83ddb70e09527208ed5afc72' 
  AND token = 'i20ePg9EPGA+eGUUDywvDYs0ukmotFrdDQtacv6FMRc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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