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 
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') 
WHERE 
  cscart_products_categories.product_id IN (
    403166, 443366, 406831, 433693, 445954, 
    441514, 409350, 459209, 410927, 406634, 
    450452, 453579, 428056, 419040, 408601, 
    433947, 418245, 450170, 460049, 430800, 
    435777, 452645, 446157, 434819, 439332, 
    410664, 457167, 442668, 438623, 443841, 
    442218, 414148, 426118, 460489, 445497, 
    420289, 445023, 406489, 425857, 423797, 
    409307, 457277, 414945, 450623, 417564, 
    405376, 423809, 415249
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00076

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.161436522,
    "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": 48,
          "cost": 0.08683616,
          "filtered": 100,
          "attached_condition": "cscart_products_categories.product_id in (403166,443366,406831,433693,445954,441514,409350,459209,410927,406634,450452,453579,428056,419040,408601,433947,418245,450170,460049,430800,435777,452645,446157,434819,439332,410664,457167,442668,438623,443841,442218,414148,426118,460489,445497,420289,445023,406489,425857,423797,409307,457277,414945,450623,417564,405376,423809,415249)",
          "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": ["u985510652_ecartify.cscart_products_categories.category_id"],
          "loops": 48,
          "rows": 1,
          "cost": 0.04375232,
          "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')"
        }
      }
    ]
  }
}