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.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 = 2712 
WHERE 
  cscart_products_categories.product_id IN (
    70149, 69350, 69997, 65553, 65832, 65096, 
    67762, 68110, 67730, 68008, 68009, 
    68052, 68065, 65122, 68039, 68071, 
    68085, 68086, 68101, 64976, 67769, 
    68057, 68058, 69972, 19741, 19744, 
    19748, 27363, 27368, 27370, 68038, 
    68089, 68099, 69999, 19742, 19743, 
    19745, 19746, 19747, 19749, 19750, 
    19751, 19752, 19753, 19754, 19755, 
    27337, 27339, 27340, 27342, 27343, 
    27345, 27359, 27360, 27361, 27364, 
    27365, 27366, 27367, 27369, 27371, 
    65124, 68068, 68129, 70000, 70001, 
    70002, 70003, 70145, 70292, 70293, 
    70294, 70297, 70298
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00248

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "159.30"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt",
              "idx_product_category_lookup",
              "idx_products_categories_composite"
            ],
            "key": "idx_products_categories_composite",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 116,
            "rows_produced_per_join": 116,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "12.13",
              "eval_cost": "11.60",
              "prefix_cost": "23.73",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`cscart_db`.`cscart_products_categories`.`product_id` in (70149,69350,69997,65553,65832,65096,67762,68110,67730,68008,68009,68052,68065,65122,68039,68071,68085,68086,68101,64976,67769,68057,68058,69972,19741,19744,19748,27363,27368,27370,68038,68089,68099,69999,19742,19743,19745,19746,19747,19749,19750,19751,19752,19753,19754,19755,27337,27339,27340,27342,27343,27345,27359,27360,27361,27364,27365,27366,27367,27369,27371,65124,68068,68129,70000,70001,70002,70003,70145,70292,70293,70294,70297,70298))"
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt",
              "idx_product_category_lookup",
              "idx_products_categories_composite"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "cscart_db.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 116,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "83.38",
              "eval_cost": "11.60",
              "prefix_cost": "118.70",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "p_category_id",
              "idx_categories_storefront_status",
              "idx_categories_usergroup_status",
              "idx_categories_status_id_path"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "cscart_db.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 95,
            "filtered": "81.96",
            "cost_info": {
              "read_cost": "29.00",
              "eval_cost": "9.51",
              "prefix_cost": "159.30",
              "data_read_per_join": "265K"
            },
            "used_columns": [
              "category_id",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`cscart_db`.`cscart_categories`.`storefront_id` in (0,1)) and (`cscart_db`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}