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 = 266 
WHERE 
  cscart_products_categories.product_id IN (
    430866, 430910, 431046, 431131, 431291, 
    381713, 339691, 430896, 430932, 431185, 
    431220, 431333, 431501, 430631, 430653, 
    430730, 430887, 430900, 431072, 431205, 
    431345, 430885, 430999, 431338, 430634, 
    430645, 430761, 430862, 430937, 430992, 
    431054, 431140, 431316, 381711, 339733, 
    339804, 430708, 430870, 431077, 431326, 
    339600, 339781, 430677, 430738, 430994, 
    339831, 430714, 430749, 430797, 430853, 
    430865, 430881, 431365, 430947, 431024, 
    431192, 431463, 430802, 430873, 430936, 
    431242, 430656, 430993, 431395, 431429, 
    339488, 430846, 430960, 431019, 431039, 
    431061, 430626, 430707, 430836, 430969, 
    431003, 431011, 431052, 431322, 430652, 
    430704, 430841, 430905, 430984, 431091, 
    431248, 431315, 430810, 431051, 431113, 
    431503, 430837, 430861, 431074, 431200, 
    431247, 431439, 431178, 431252, 431487
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00294

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 (430866,430910,431046,431131,431291,381713,339691,430896,430932,431185,431220,431333,431501,430631,430653,430730,430887,430900,431072,431205,431345,430885,430999,431338,430634,430645,430761,430862,430937,430992,431054,431140,431316,381711,339733,339804,430708,430870,431077,431326,339600,339781,430677,430738,430994,339831,430714,430749,430797,430853,430865,430881,431365,430947,431024,431192,431463,430802,430873,430936,431242,430656,430993,431395,431429,339488,430846,430960,431019,431039,431061,430626,430707,430836,430969,431003,431011,431052,431322,430652,430704,430841,430905,430984,431091,431248,431315,430810,431051,431113,431503,430837,430861,431074,431200,431247,431439,431178,431252,431487))"
          }
        },
        {
          "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')))"
          }
        }
      ]
    }
  }
}