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 = 301 
WHERE 
  cscart_products_categories.product_id IN (
    12995, 12996, 12997, 12998, 15744, 15745, 
    15746, 15743, 15738, 15739, 15740, 
    15741, 15742, 15736, 15737, 12999, 
    13000, 13001, 13002, 13003, 13004, 
    13005, 13006, 13007, 13008, 13009, 
    13010, 13011, 13012, 12969, 13013, 
    13014, 13015, 13016, 13017, 13018, 
    13019, 13020, 13021, 13022, 13023, 
    13024, 13025, 13026, 13027, 13028, 
    13029, 13030, 13031, 13032, 13033, 
    13034, 13035, 13036, 13037, 13038, 
    13039, 13040, 13041, 13042, 13043, 
    13044
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00170

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": 139,
      "filtered": 100,
      "index_condition": "cscart_products_categories.product_id in (12995,12996,12997,12998,15744,15745,15746,15743,15738,15739,15740,15741,15742,15736,15737,12999,13000,13001,13002,13003,13004,13005,13006,13007,13008,13009,13010,13011,13012,12969,13013,13014,13015,13016,13017,13018,13019,13020,13021,13022,13023,13024,13025,13026,13027,13028,13029,13030,13031,13032,13033,13034,13035,13036,13037,13038,13039,13040,13041,13042,13043,13044)"
    },
    "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')"
    }
  }
}