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, 2) 
  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 = 523 
WHERE 
  cscart_products_categories.product_id IN (
    4793, 4794, 4796, 4797, 4799, 4800, 4801, 
    4802, 4803, 4804, 4805, 4806, 4807, 
    4808, 4809, 4810, 4811, 4813, 4814, 
    4815, 4816, 4817, 4818, 4819, 4821, 
    4822, 4823
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00123

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "26.73"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "0.37"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 35,
            "rows_produced_per_join": 1,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "4.04",
              "eval_cost": "0.14",
              "prefix_cost": "4.18",
              "data_read_per_join": "6K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`primapearl_r_new`.`cscart_categories`.`storefront_id` in (0,2)) and ((`primapearl_r_new`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`primapearl_r_new`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`primapearl_r_new`.`cscart_categories`.`usergroup_ids`))) and (`primapearl_r_new`.`cscart_categories`.`status` in ('A','H')))"
          }
        },
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "primapearl_r_new.cscart_categories.category_id"
            ],
            "rows_examined_per_scan": 45,
            "rows_produced_per_join": 0,
            "filtered": "0.59",
            "index_condition": "(`primapearl_r_new`.`cscart_products_categories`.`product_id` in (4793,4794,4796,4797,4799,4800,4801,4802,4803,4804,4805,4806,4807,4808,4809,4810,4811,4813,4814,4815,4816,4817,4818,4819,4821,4822,4823))",
            "cost_info": {
              "read_cost": "15.75",
              "eval_cost": "0.04",
              "prefix_cost": "26.23",
              "data_read_per_join": "5"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "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",
              "primapearl_r_new.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.09",
              "eval_cost": "0.04",
              "prefix_cost": "26.36",
              "data_read_per_join": "5"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}