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 (
    286, 278, 280, 282, 247, 255, 256, 257, 
    249, 250, 251, 252, 253, 254, 248, 245, 
    246, 66, 166, 192, 194, 195, 196, 197, 
    198, 199, 200, 201, 202, 203, 204, 230, 
    231, 232, 233, 234, 235, 236, 237, 238, 
    239, 78, 79, 80, 81, 82, 83, 84, 85, 86, 
    87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 
    97, 100, 101, 102
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00151

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "read_sorted_file": {
          "filesort": {
            "sort_key": "cscart_products_categories.product_id",
            "table": {
              "table_name": "cscart_products_categories",
              "access_type": "ALL",
              "possible_keys": ["PRIMARY", "pt"],
              "rows": 281,
              "filtered": 24.91103172,
              "attached_condition": "cscart_products_categories.product_id in (286,278,280,282,247,255,256,257,249,250,251,252,253,254,248,245,246,66,166,192,194,195,196,197,198,199,200,201,202,203,204,230,231,232,233,234,235,236,237,238,239,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,100,101,102)"
            }
          }
        }
      },
      {
        "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": ["cscart.cscart_products_categories.category_id"],
          "rows": 1,
          "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')"
        }
      }
    ]
  }
}