SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids, 
  product_position_source.position AS position 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.storefront_id IN (0, 1) 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 266 
WHERE 
  cscart_products_categories.product_id IN (
    339769, 430915, 431100, 430803, 339750, 
    339829, 430747, 430748, 430916, 430924, 
    431195, 431203, 339695, 339714, 339735, 
    431176, 431196, 431204, 381701, 430648, 
    431133, 431158, 339807, 430636, 381702, 
    430823, 431199, 339752, 339746, 381687, 
    430848, 430903, 431122, 430831, 387047, 
    431139, 339452, 339654, 339479, 339755, 
    431150, 339847, 339656, 430665, 339712, 
    431145, 430696, 431102, 430771, 430907, 
    430649, 339851, 430912, 430638, 430646, 
    430647, 339715, 430935, 339648, 339668, 
    339485, 339729, 381696, 431097, 339671, 
    339681, 339655, 431151, 339760, 431201, 
    430766, 430821, 339664, 339694, 430824, 
    431068, 431359, 339828, 339809, 430857, 
    339812, 339817, 430746, 430813, 339761, 
    339650, 339697, 430925, 431103, 431163, 
    339720, 431085, 431164, 430817, 430902, 
    339835, 430654, 431313, 431053, 431120
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00328

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "281.15"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 100,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "21.15",
              "eval_cost": "20.00",
              "prefix_cost": "41.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (339769,430915,431100,430803,339750,339829,430747,430748,430916,430924,431195,431203,339695,339714,339735,431176,431196,431204,381701,430648,431133,431158,339807,430636,381702,430823,431199,339752,339746,381687,430848,430903,431122,430831,387047,431139,339452,339654,339479,339755,431150,339847,339656,430665,339712,431145,430696,431102,430771,430907,430649,339851,430912,430638,430646,430647,339715,430935,339648,339668,339485,339729,381696,431097,339671,339681,339655,431151,339760,431201,430766,430821,339664,339694,430824,431068,431359,339828,339809,430857,339812,339817,430746,430813,339761,339650,339697,430925,431103,431163,339720,431085,431164,430817,430902,339835,430654,431313,431053,431120))"
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "webmarco.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "20.00",
              "prefix_cost": "161.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "webmarco.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 5,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "1.00",
              "prefix_cost": "281.15",
              "data_read_per_join": "29K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`webmarco`.`cscart_categories`.`storefront_id` in (0,1)) and ((`webmarco`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`webmarco`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`webmarco`.`cscart_categories`.`usergroup_ids`)) and (`webmarco`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}