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 (
    430995, 431290, 431004, 431087, 430983, 
    431071, 431231, 431405, 431497, 431381, 
    431411, 431017, 431182, 431274, 431434, 
    430686, 430974, 431045, 431175, 430765, 
    430785, 431001, 431494, 431495, 430762, 
    430965, 431403, 431465, 381710, 430963, 
    431002, 431025, 431240, 431329, 381707, 
    430755, 430964, 430966, 431457, 430630, 
    430752, 430773, 431304, 431284, 431425, 
    431328, 430711, 430961, 431235, 431343, 
    431362, 431422, 431498, 431505, 431079, 
    431355, 431394, 431408, 431243, 431260, 
    431383, 431407, 430759, 431015, 431283, 
    431488, 430669, 430700, 430943, 430971, 
    431105, 431152, 431340, 431352, 431409, 
    430944, 431018, 431057, 431069, 431217, 
    431337, 430705, 430929, 430978, 431030, 
    431419, 430717, 430781, 431311, 431346, 
    431427, 435510, 430938, 430956, 431302, 
    431482, 431500, 431415, 431453, 430732
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00343

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "283.96"
    },
    "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": 101,
            "rows_produced_per_join": 101,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "21.36",
              "eval_cost": "20.20",
              "prefix_cost": "41.56",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (430995,431290,431004,431087,430983,431071,431231,431405,431497,431381,431411,431017,431182,431274,431434,430686,430974,431045,431175,430765,430785,431001,431494,431495,430762,430965,431403,431465,381710,430963,431002,431025,431240,431329,381707,430755,430964,430966,431457,430630,430752,430773,431304,431284,431425,431328,430711,430961,431235,431343,431362,431422,431498,431505,431079,431355,431394,431408,431243,431260,431383,431407,430759,431015,431283,431488,430669,430700,430943,430971,431105,431152,431340,431352,431409,430944,431018,431057,431069,431217,431337,430705,430929,430978,431030,431419,430717,430781,431311,431346,431427,435510,430938,430956,431302,431482,431500,431415,431453,430732))"
          }
        },
        {
          "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": 101,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "101.00",
              "eval_cost": "20.20",
              "prefix_cost": "162.76",
              "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": "101.00",
              "eval_cost": "1.01",
              "prefix_cost": "283.96",
              "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')))"
          }
        }
      ]
    }
  }
}