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 (
    36394, 36411, 36396, 36462, 36398, 36410, 
    36405, 36490, 36477, 36434, 36460, 
    36403, 36399, 36422, 36397, 36419, 
    36487, 36491, 36471, 36409, 36404, 
    36423, 36414, 36408, 36412, 36439, 
    36406, 36469, 36415, 36413, 36428, 
    36402, 36443, 36417, 36427, 36416, 
    36448, 36426, 36453, 36467, 36457, 
    36437, 36421, 36461, 36463, 36407, 
    36436, 36420, 36401, 36447, 36430, 
    36438, 36485, 36435, 36459, 36451, 
    36492, 36449, 36458, 36486, 36441, 
    36472, 36446, 36424, 36425, 36454, 
    36481, 36483, 36464, 36475, 36482, 
    36473, 36493, 36444, 36479, 36445, 
    36431, 36456, 36470, 36466, 36474, 
    36478, 36440, 36452, 36465, 36442, 
    36450, 36433, 36484, 36418, 36429, 
    36432, 36400, 36476, 36395, 36488, 
    36494, 36455, 36480, 36489, 36468
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00281

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "176.46"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 189,
            "rows_produced_per_join": 189,
            "filtered": "100.00",
            "index_condition": "(`cscartdb`.`cscart_products_categories`.`product_id` in (36394,36411,36396,36462,36398,36410,36405,36490,36477,36434,36460,36403,36399,36422,36397,36419,36487,36491,36471,36409,36404,36423,36414,36408,36412,36439,36406,36469,36415,36413,36428,36402,36443,36417,36427,36416,36448,36426,36453,36467,36457,36437,36421,36461,36463,36407,36436,36420,36401,36447,36430,36438,36485,36435,36459,36451,36492,36449,36458,36486,36441,36472,36446,36424,36425,36454,36481,36483,36464,36475,36482,36473,36493,36444,36479,36445,36431,36456,36470,36466,36474,36478,36440,36452,36465,36442,36450,36433,36484,36418,36429,36432,36400,36476,36395,36488,36494,36455,36480,36489,36468))",
            "cost_info": {
              "read_cost": "91.41",
              "eval_cost": "18.90",
              "prefix_cost": "110.31",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "cscartdb.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 9,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "47.25",
              "eval_cost": "0.95",
              "prefix_cost": "176.46",
              "data_read_per_join": "31K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`cscartdb`.`cscart_categories`.`storefront_id` in (0,1)) and ((`cscartdb`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`cscartdb`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`cscartdb`.`cscart_categories`.`usergroup_ids`))) and (`cscartdb`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}