SELECT 
  category_id, 
  parent_id 
FROM 
  cscart_categories 
WHERE 
  parent_id IN(
    3123, 3124, 3161, 3120, 3121, 3122, 3162, 
    3125, 3163, 3164, 3165, 3126, 3127, 
    3128, 3166, 3129, 3167, 3168, 3169, 
    3130, 3170, 3131, 3132, 3171, 3172, 
    3173, 3133, 3134, 3135, 3136, 3137, 
    3174, 3175, 3176, 3177, 3724, 3728
  )

Query time 0.00076

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "22.65"
    },
    "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": 54,
      "rows_produced_per_join": 54,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "11.85",
        "eval_cost": "10.80",
        "prefix_cost": "22.65",
        "data_read_per_join": "320K"
      },
      "used_columns": [
        "category_id",
        "parent_id"
      ],
      "attached_condition": "(`webmarco`.`cscart_categories`.`parent_id` in (3123,3124,3161,3120,3121,3122,3162,3125,3163,3164,3165,3126,3127,3128,3166,3129,3167,3168,3169,3130,3170,3131,3132,3171,3172,3173,3133,3134,3135,3136,3137,3174,3175,3176,3177,3724,3728))"
    }
  }
}