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, 
  product_position_source.position AS position 
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') 
  LEFT JOIN cscart_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 7 
WHERE 
  cscart_products_categories.product_id IN (
    6303, 6304, 5801, 5802, 5800, 5799, 5803, 
    5804, 7197, 7195, 7196, 7190, 7189, 
    7194, 7191, 5032, 5033, 7674, 7675, 
    6967, 6966, 6645, 6644, 6647, 6648, 
    4352, 4354, 5391, 5392, 5388, 5390, 
    5389, 5396, 5395, 5394, 5034, 5035, 
    5030, 5031, 5168, 5169, 6982, 6132, 
    7150, 7149, 7148, 7151, 6768
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00420

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "239.27"
    },
    "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": 278,
            "rows_produced_per_join": 278,
            "filtered": "100.00",
            "index_condition": "(`dbggbern`.`cscart_products_categories`.`product_id` in (6303,6304,5801,5802,5800,5799,5803,5804,7197,7195,7196,7190,7189,7194,7191,5032,5033,7674,7675,6967,6966,6645,6644,6647,6648,4352,4354,5391,5392,5388,5390,5389,5396,5395,5394,5034,5035,5030,5031,5168,5169,6982,6132,7150,7149,7148,7151,6768))",
            "cost_info": {
              "read_cost": "109.31",
              "eval_cost": "27.80",
              "prefix_cost": "137.11",
              "data_read_per_join": "4K"
            },
            "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": [
              "dbggbern.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 13,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "69.50",
              "eval_cost": "1.39",
              "prefix_cost": "234.41",
              "data_read_per_join": "55K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`dbggbern`.`cscart_categories`.`storefront_id` in (0,1)) and ((`dbggbern`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`dbggbern`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`dbggbern`.`cscart_categories`.`usergroup_ids`))) and (`dbggbern`.`cscart_categories`.`status` in ('A','H')))"
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "dbggbern.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 13,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "3.48",
              "eval_cost": "1.39",
              "prefix_cost": "239.28",
              "data_read_per_join": "222"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}