SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    2999, 2862, 2944, 2739, 3030, 3001, 2740, 
    2980, 2741, 2686, 2920, 2811, 2819, 
    2828, 2813, 2805, 2695, 2831, 2818, 
    2814, 2699, 2821, 2816, 2804, 2710, 
    2693, 2833, 2823, 2812, 2689, 2820, 
    2806, 2702, 2815, 2825, 2817, 2832, 
    2706, 2701, 2826, 2827, 2822, 2705, 
    2923, 3025, 2708, 3002, 2698, 2690, 
    2738, 2834
  )

Query time 0.00061

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "52.81"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": [
        "parent"
      ],
      "key": "parent",
      "used_key_parts": [
        "parent_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 89,
      "rows_produced_per_join": 89,
      "filtered": "100.00",
      "index_condition": "(`cscart_db`.`cscart_categories`.`parent_id` in (2999,2862,2944,2739,3030,3001,2740,2980,2741,2686,2920,2811,2819,2828,2813,2805,2695,2831,2818,2814,2699,2821,2816,2804,2710,2693,2833,2823,2812,2689,2820,2806,2702,2815,2825,2817,2832,2706,2701,2826,2827,2822,2705,2923,3025,2708,3002,2698,2690,2738,2834))",
      "cost_info": {
        "read_cost": "43.91",
        "eval_cost": "8.90",
        "prefix_cost": "52.81",
        "data_read_per_join": "248K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ]
    }
  }
}