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 = 13 
WHERE 
  cscart_products_categories.product_id IN (
    1675, 1931, 1544, 1845, 1540, 1512, 1525, 
    1536, 1538, 1937, 1581, 1582, 1838, 
    1938, 1830, 1514, 1835, 1678, 1693, 
    1711, 1699, 1698, 1869, 1834, 1833, 
    1928, 1537, 1539, 1436, 1411, 1397, 
    1741, 1330, 1486, 1546, 1651, 1661, 
    255, 1742, 1598, 1565, 1597, 1708, 1694, 
    1732, 1596, 1632, 1618
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00185

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": 49,
      "filtered": 100,
      "index_condition": "cscart_products_categories.product_id in (1675,1931,1544,1845,1540,1512,1525,1536,1538,1937,1581,1582,1838,1938,1830,1514,1835,1678,1693,1711,1699,1698,1869,1834,1833,1928,1537,1539,1436,1411,1397,1741,1330,1486,1546,1651,1661,255,1742,1598,1565,1597,1708,1694,1732,1596,1632,1618)"
    },
    "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": ["bacpvdev_db.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')"
    },
    "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", "bacpvdev_db.cscart_products_categories.product_id"],
      "rows": 1,
      "filtered": 100
    }
  }
}