SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    1850, 1856, 1843, 1865, 1861, 1844, 1862, 
    1851, 1857, 1849, 1852, 1846, 1858, 
    1863, 1860, 1853, 1859, 1847, 1855, 
    1854, 1804, 1864, 1983
  )

Query time 0.00043

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": 38,
      "filtered": 100,
      "attached_condition": "cscart_categories.parent_id in (1850,1856,1843,1865,1861,1844,1862,1851,1857,1849,1852,1846,1858,1863,1860,1853,1859,1847,1855,1854,1804,1864,1983)",
      "using_index": true
    }
  }
}

Result