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 (
    278, 280, 282, 247, 248, 241, 244, 245, 
    246, 240, 6, 66, 166, 214, 219, 221, 223, 
    192, 194, 195, 196, 197, 198, 199, 200, 
    201, 202, 203, 204, 205, 206, 207, 208, 
    209, 210, 211, 212, 213, 215, 217, 218, 
    220, 222, 224, 225, 226, 227, 228, 229, 
    230, 231, 232, 233, 234, 235, 236, 237, 
    238, 239, 242, 243, 78, 79, 80, 81, 82, 
    83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 
    93, 94, 95, 96, 97, 100, 101, 102, 103, 
    104, 105, 106, 107, 108, 109, 110, 111, 
    112, 113, 114
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00106

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "41.62"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "3.83"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 98,
            "rows_produced_per_join": 3,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "22.50",
              "eval_cost": "0.78",
              "prefix_cost": "23.28",
              "data_read_per_join": "13K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`danishecarter_31jan`.`cscart_categories`.`storefront_id` in (0,1)) and ((`danishecarter_31jan`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`danishecarter_31jan`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`danishecarter_31jan`.`cscart_categories`.`usergroup_ids`)) and (`danishecarter_31jan`.`cscart_categories`.`status` in ('A','H')))"
          }
        },
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "danishecarter_31jan.cscart_categories.category_id"
            ],
            "rows_examined_per_scan": 3,
            "rows_produced_per_join": 3,
            "filtered": "32.58",
            "index_condition": "(`danishecarter_31jan`.`cscart_products_categories`.`product_id` in (278,280,282,247,248,241,244,245,246,240,6,66,166,214,219,221,223,192,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,215,217,218,220,222,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,242,243,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114))",
            "cost_info": {
              "read_cost": "12.15",
              "eval_cost": "0.77",
              "prefix_cost": "37.79",
              "data_read_per_join": "61"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        }
      ]
    }
  }
}