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 = 291 
WHERE 
  cscart_products_categories.product_id IN (
    12995, 12996, 12997, 12998, 10713, 10714, 
    10715, 10716, 10717, 10718, 10719, 
    10720, 10721, 10722, 10723, 10305, 
    10306, 10307, 10308, 10309, 10310, 
    10311, 10312, 12999, 13000, 13001, 
    13002, 13003, 13004, 13005, 13006, 
    13007, 13008, 13009, 13010, 13011, 
    13012, 9874, 9875, 9887, 9879, 9796, 
    9942, 9943, 9941, 9944, 10813, 10814, 
    10815, 10816, 10817, 10818, 10819, 
    10820, 10821, 10822, 10823, 10824, 
    10825, 10826, 10704, 10705, 10706, 
    10707
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00202

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products_categories",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "pt"],
      "key": "pt",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 64,
      "filtered": 100,
      "index_condition": "cscart_products_categories.product_id in (12995,12996,12997,12998,10713,10714,10715,10716,10717,10718,10719,10720,10721,10722,10723,10305,10306,10307,10308,10309,10310,10311,10312,12999,13000,13001,13002,13003,13004,13005,13006,13007,13008,13009,13010,13011,13012,9874,9875,9887,9879,9796,9942,9943,9941,9944,10813,10814,10815,10816,10817,10818,10819,10820,10821,10822,10823,10824,10825,10826,10704,10705,10706,10707)"
    },
    "table": {
      "table_name": "product_position_source",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "pt"],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["category_id", "product_id"],
      "ref": [
        "const",
        "noframes_angrybeaver.cscart_products_categories.product_id"
      ],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "c_status", "p_category_id"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "ref": ["noframes_angrybeaver.cscart_products_categories.category_id"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "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')"
    }
  }
}