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 (
    48, 54, 44, 194, 137, 153, 164, 236, 234, 
    150, 151, 178, 181, 248, 65, 64, 63, 62, 
    66, 140, 141, 144, 143, 142
  ) 
GROUP BY 
  cscart_aprilproducts_categories.product_id

Query time 0.00100

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "31.20"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "0.65"
      },
      "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": "9.70",
            "index_condition": "(`vishalecarter_april_setup`.`cscart_aprilproducts_categories`.`product_id` in (48,54,44,194,137,153,164,236,234,150,151,178,181,248,65,64,63,62,66,140,141,144,143,142))",
            "cost_info": {
              "read_cost": "9.00",
              "eval_cost": "0.13",
              "prefix_cost": "30.55",
              "data_read_per_join": "10"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        }
      ]
    }
  }
}

Result

product_id category_ids
44 221M
48 186M
54 202M
62 189M
63 189M
64 189M
65 189M
66 189M
137 249M
140 180M
141 180M
142 180M
143 180M
144 180M
150 210M
151 210M
153 181M
164 199,198M
178 252M
181 212M
194 232M
234 217M
236 218M
248 255,248M