SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    1618, 1684, 1663, 1647, 1682, 1672, 1662, 
    1644, 1671, 1652, 1650, 1683, 1660, 
    1655, 1654, 1680, 1645, 1679, 313
  )

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": ["parent"],
      "key": "parent",
      "key_length": "3",
      "used_key_parts": ["parent_id"],
      "rows": 19,
      "filtered": 100,
      "index_condition": "cscart_categories.parent_id in (1618,1684,1663,1647,1682,1672,1662,1644,1671,1652,1650,1683,1660,1655,1654,1680,1645,1679,313)"
    }
  }
}