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 = 445 
WHERE 
  cscart_products_categories.product_id IN (
    315850, 315943, 316618, 323594, 323621, 
    324557, 73605, 87023, 265180, 300746, 
    305637, 312771, 323588, 324430, 325131, 
    325407, 228357, 261812, 293942, 301454, 
    311274, 312663, 323303, 323592, 323617, 
    323627, 325112, 325133, 265183, 286299, 
    292637, 305636, 323586, 323587, 326296, 
    327385, 328466, 302560, 305634, 305635, 
    311273, 312778, 312795, 312812, 315904, 
    323590, 323591, 323593, 323868, 325122, 
    325132, 325561, 227930, 300730, 305638, 
    323589, 325842, 328159, 300747, 312765, 
    312793, 312794, 315903, 325109, 330705, 
    306671, 312633, 324549, 185419, 269163, 
    273172, 299568, 300753, 302068, 312659, 
    325126, 327998, 328311, 185033, 229515
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00306

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "84.37"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt",
              "position",
              "category_position"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 80,
            "rows_produced_per_join": 80,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "8.29",
              "eval_cost": "8.00",
              "prefix_cost": "16.29",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`unicomps`.`cscart_products_categories`.`product_id` in (315850,315943,316618,323594,323621,324557,73605,87023,265180,300746,305637,312771,323588,324430,325131,325407,228357,261812,293942,301454,311274,312663,323303,323592,323617,323627,325112,325133,265183,286299,292637,305636,323586,323587,326296,327385,328466,302560,305634,305635,311273,312778,312795,312812,315904,323590,323591,323593,323868,325122,325132,325561,227930,300730,305638,323589,325842,328159,300747,312765,312793,312794,315903,325109,330705,306671,312633,324549,185419,269163,273172,299568,300753,302068,312659,325126,327998,328311,185033,229515))"
          }
        },
        {
          "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",
              "unicomps.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 80,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "32.08",
              "eval_cost": "8.00",
              "prefix_cost": "56.37",
              "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",
              "storefront_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "unicomps.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 15,
            "filtered": "19.97",
            "cost_info": {
              "read_cost": "20.00",
              "eval_cost": "1.60",
              "prefix_cost": "84.37",
              "data_read_per_join": "65K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`unicomps`.`cscart_categories`.`storefront_id` in (0,1)) and ((`unicomps`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`unicomps`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`unicomps`.`cscart_categories`.`usergroup_ids`))) and (`unicomps`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}