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 = 9 
WHERE 
  cscart_products_categories.product_id IN (
    7676, 7683, 7298, 7297, 5968, 2639, 5113, 
    7295, 7772, 7771, 7294, 7296, 2640, 
    7768, 7759, 7867, 7758, 7868, 2641, 
    7317, 7320, 7321, 2642, 5112, 3141, 
    7318, 3142, 2643, 3143, 7760, 7761, 
    7762, 3144, 5414, 5411, 5413, 5412, 
    5415, 4321, 4320, 4323, 4322, 4324, 
    4325, 4337, 4338, 4340, 4339
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00279

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "148.53"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 167,
            "rows_produced_per_join": 167,
            "filtered": "100.00",
            "index_condition": "(`dbggbern`.`cscart_products_categories`.`product_id` in (7676,7683,7298,7297,5968,2639,5113,7295,7772,7771,7294,7296,2640,7768,7759,7867,7758,7868,2641,7317,7320,7321,2642,5112,3141,7318,3142,2643,3143,7760,7761,7762,3144,5414,5411,5413,5412,5415,4321,4320,4323,4322,4324,4325,4337,4338,4340,4339))",
            "cost_info": {
              "read_cost": "70.46",
              "eval_cost": "16.70",
              "prefix_cost": "87.16",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "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": [
              "dbggbern.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 8,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "41.75",
              "eval_cost": "0.84",
              "prefix_cost": "145.61",
              "data_read_per_join": "33K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`dbggbern`.`cscart_categories`.`storefront_id` in (0,1)) and ((`dbggbern`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`dbggbern`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`dbggbern`.`cscart_categories`.`usergroup_ids`))) and (`dbggbern`.`cscart_categories`.`status` in ('A','H')))"
          }
        },
        {
          "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",
              "dbggbern.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 8,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "2.09",
              "eval_cost": "0.84",
              "prefix_cost": "148.53",
              "data_read_per_join": "133"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}