SELECT 
  cscart_aprilproducts_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_aprilproducts_categories.link_type = "M", 
      CONCAT(
        cscart_aprilproducts_categories.category_id, 
        "M"
      ), 
      cscart_aprilproducts_categories.category_id
    )
  ) AS category_ids 
FROM 
  cscart_aprilproducts_categories 
  INNER JOIN cscart_aprilcategories ON cscart_aprilcategories.category_id = cscart_aprilproducts_categories.category_id 
  AND cscart_aprilcategories.storefront_id IN (0, 1) 
  AND (
    cscart_aprilcategories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_aprilcategories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_aprilcategories.usergroup_ids
    )
  ) 
  AND cscart_aprilcategories.status IN ('A', 'H') 
WHERE 
  cscart_aprilproducts_categories.product_id IN (
    280, 282, 278, 20, 119, 100, 46, 204, 45, 
    68, 29, 6, 8, 14, 9, 10, 19, 21, 7, 27, 124, 
    50, 51, 49
  ) 
GROUP BY 
  cscart_aprilproducts_categories.product_id

Query time 0.00097

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "31.32"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "0.78"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_aprilcategories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 84,
            "rows_produced_per_join": 3,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "19.53",
              "eval_cost": "0.67",
              "prefix_cost": "20.20",
              "data_read_per_join": "8K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`vishalecarter_april_setup`.`cscart_aprilcategories`.`storefront_id` in (0,1)) and ((`vishalecarter_april_setup`.`cscart_aprilcategories`.`usergroup_ids` = '') or find_in_set(0,`vishalecarter_april_setup`.`cscart_aprilcategories`.`usergroup_ids`) or find_in_set(1,`vishalecarter_april_setup`.`cscart_aprilcategories`.`usergroup_ids`)) and (`vishalecarter_april_setup`.`cscart_aprilcategories`.`status` in ('A','H')))"
          }
        },
        {
          "table": {
            "table_name": "cscart_aprilproducts_categories",
            "access_type": "ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "vishalecarter_april_setup.cscart_aprilcategories.category_id"
            ],
            "rows_examined_per_scan": 2,
            "rows_produced_per_join": 0,
            "filtered": "11.57",
            "index_condition": "(`vishalecarter_april_setup`.`cscart_aprilproducts_categories`.`product_id` in (280,282,278,20,119,100,46,204,45,68,29,6,8,14,9,10,19,21,7,27,124,50,51,49))",
            "cost_info": {
              "read_cost": "9.00",
              "eval_cost": "0.16",
              "prefix_cost": "30.55",
              "data_read_per_join": "12"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        }
      ]
    }
  }
}