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 = 20 
WHERE 
  cscart_products_categories.product_id IN (
    99, 97, 98, 91, 96, 182, 451, 454, 453, 
    457, 701, 702, 708, 228, 452, 447, 829, 
    769, 831, 818, 847, 774, 833, 368, 432, 
    433, 434, 435, 436, 437, 438, 439, 440, 
    441, 442, 443, 444, 445, 446, 369, 417, 
    418, 419, 420, 421, 422, 423, 424
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00073

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.178653694,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_products_categories",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "pt"],
          "key": "pt",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "loops": 1,
          "rows": 52,
          "cost": 0.0489205,
          "filtered": 100,
          "attached_condition": "cscart_products_categories.product_id in (99,97,98,91,96,182,451,454,453,457,701,702,708,228,452,447,829,769,831,818,847,774,833,368,432,433,434,435,436,437,438,439,440,441,442,443,444,445,446,369,417,418,419,420,421,422,423,424)",
          "using_index": true
        }
      },
      {
        "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": [
            "u428615623_ecartifygonje.cscart_products_categories.category_id"
          ],
          "loops": 52,
          "rows": 1,
          "cost": 0.04733008,
          "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",
            "u428615623_ecartifygonje.cscart_products_categories.product_id"
          ],
          "loops": 52,
          "rows": 1,
          "cost": 0.04896848,
          "filtered": 100
        }
      }
    ]
  }
}