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 = 2910 
WHERE 
  cscart_products_categories.product_id IN (
    356857, 357446, 359239, 350620, 350984, 
    352917, 353399, 356900, 358338, 350309, 
    353610, 354728, 350229, 350742, 351676, 
    352522, 353366, 354011, 354588, 354704, 
    356925, 356965, 357318, 357817, 358076, 
    349833, 351402, 351566, 352188, 352490, 
    352928, 353015, 354506, 354819, 356370, 
    357163, 349859, 350660, 351209, 355302, 
    356337, 351479, 352968, 353475, 355268, 
    356430, 351214, 351430, 355848, 357712, 
    358033, 359020, 359087, 349720, 349725, 
    352106, 352744, 356760, 357577, 358534, 
    359106, 354314, 355171, 356202, 356856, 
    357679, 359407, 350328, 351821, 353503, 
    359090, 349933, 349945, 350679, 353319, 
    353354, 353553, 353665, 354857, 355777, 
    358155, 358977, 352629, 352902, 353003, 
    353548, 353728, 354076, 354666, 354686, 
    358304, 350171, 350808, 351046, 351374, 
    352198, 352915, 352964, 355521, 355596
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00293

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "281.15"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 100,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "21.15",
              "eval_cost": "20.00",
              "prefix_cost": "41.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (356857,357446,359239,350620,350984,352917,353399,356900,358338,350309,353610,354728,350229,350742,351676,352522,353366,354011,354588,354704,356925,356965,357318,357817,358076,349833,351402,351566,352188,352490,352928,353015,354506,354819,356370,357163,349859,350660,351209,355302,356337,351479,352968,353475,355268,356430,351214,351430,355848,357712,358033,359020,359087,349720,349725,352106,352744,356760,357577,358534,359106,354314,355171,356202,356856,357679,359407,350328,351821,353503,359090,349933,349945,350679,353319,353354,353553,353665,354857,355777,358155,358977,352629,352902,353003,353548,353728,354076,354666,354686,358304,350171,350808,351046,351374,352198,352915,352964,355521,355596))"
          }
        },
        {
          "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",
              "webmarco.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "20.00",
              "prefix_cost": "161.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "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": [
              "webmarco.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 5,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "1.00",
              "prefix_cost": "281.15",
              "data_read_per_join": "29K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`webmarco`.`cscart_categories`.`storefront_id` in (0,1)) and ((`webmarco`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`webmarco`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`webmarco`.`cscart_categories`.`usergroup_ids`)) and (`webmarco`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}