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 = 265 
WHERE 
  cscart_products_categories.product_id IN (
    12684, 12714, 13260, 13267, 13176, 13162, 
    13169, 13232, 13225, 13190, 13183, 
    13239, 13204, 13197, 13246, 13218, 
    13211, 13253, 13302, 13303, 13308, 
    13309, 13306, 13307, 13310, 13311, 
    13312, 13313, 13304, 13305, 12349, 
    12364, 12259, 12504, 12524, 12379, 
    13319, 1154, 3315, 6843, 3318, 3687, 
    5076, 6840, 4691, 3071, 513, 3505
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00287

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "60.14"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "1.01"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 46,
            "rows_produced_per_join": 1,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "5.15",
              "eval_cost": "0.18",
              "prefix_cost": "5.33",
              "data_read_per_join": "7K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`test2_gaseus`.`cscart_categories`.`storefront_id` in (0,1)) and ((`test2_gaseus`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`test2_gaseus`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`test2_gaseus`.`cscart_categories`.`usergroup_ids`))) and (`test2_gaseus`.`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": [
              "test2_gaseus.cscart_categories.category_id"
            ],
            "rows_examined_per_scan": 83,
            "rows_produced_per_join": 1,
            "filtered": "0.66",
            "index_condition": "(`test2_gaseus`.`cscart_products_categories`.`product_id` in (12684,12714,13260,13267,13176,13162,13169,13232,13225,13190,13183,13239,13204,13197,13246,13218,13211,13253,13302,13303,13308,13309,13306,13307,13310,13311,13312,13313,13304,13305,12349,12364,12259,12504,12524,12379,13319,1154,3315,6843,3318,3687,5076,6840,4691,3071,513,3505))",
            "cost_info": {
              "read_cost": "38.18",
              "eval_cost": "0.10",
              "prefix_cost": "58.78",
              "data_read_per_join": "16"
            },
            "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",
              "test2_gaseus.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.25",
              "eval_cost": "0.10",
              "prefix_cost": "59.14",
              "data_read_per_join": "16"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}