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 (
    13029, 13030, 10106, 10105, 10104, 10103, 
    10625, 10626, 10627, 10628, 10629, 
    10630, 10631, 10632, 10633, 10634, 
    10635, 10636, 10403, 10404, 10405, 
    15781, 10406, 10407, 10408, 10409, 
    10410, 10411, 10412, 12853, 12854, 
    12855, 10414, 10415, 10416, 12856, 
    10417, 10418, 10419, 10420, 10421, 
    10422, 10423, 10424, 10384, 10383, 
    10382, 10753, 10754, 10755, 10296, 
    10297, 10298, 10299, 10300, 10446, 
    10756, 10757, 10758, 13031, 13032, 
    13033, 13034, 13035
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00214

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": 67,
      "filtered": 100,
      "index_condition": "cscart_products_categories.product_id in (13029,13030,10106,10105,10104,10103,10625,10626,10627,10628,10629,10630,10631,10632,10633,10634,10635,10636,10403,10404,10405,15781,10406,10407,10408,10409,10410,10411,10412,12853,12854,12855,10414,10415,10416,12856,10417,10418,10419,10420,10421,10422,10423,10424,10384,10383,10382,10753,10754,10755,10296,10297,10298,10299,10300,10446,10756,10757,10758,13031,13032,13033,13034,13035)"
    },
    "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')"
    }
  }
}