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 = 316 
WHERE 
  cscart_products_categories.product_id IN (
    31913, 31915, 31924, 31902, 31909, 31899, 
    31916, 31922, 31928, 31930, 31932, 
    31903, 31917, 31905, 31914, 31918, 
    31919, 31921, 31964, 31839, 31842, 
    31845, 31908, 31910, 31911, 31912, 
    31925, 31931, 31933, 31934
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00211

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "166.81"
    },
    "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": 36,
            "rows_produced_per_join": 36,
            "filtered": "100.00",
            "index_condition": "(`ea201_diorama`.`cscart_products_categories`.`product_id` in (31913,31915,31924,31902,31909,31899,31916,31922,31928,31930,31932,31903,31917,31905,31914,31918,31919,31921,31964,31839,31842,31845,31908,31910,31911,31912,31925,31931,31933,31934))",
            "cost_info": {
              "read_cost": "73.21",
              "eval_cost": "7.20",
              "prefix_cost": "80.41",
              "data_read_per_join": "576"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "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",
              "ea201_diorama.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 36,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "36.00",
              "eval_cost": "7.20",
              "prefix_cost": "123.61",
              "data_read_per_join": "576"
            },
            "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": [
              "ea201_diorama.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "36.00",
              "eval_cost": "0.36",
              "prefix_cost": "166.81",
              "data_read_per_join": "4K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`ea201_diorama`.`cscart_categories`.`storefront_id` in (0,1)) and ((`ea201_diorama`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`ea201_diorama`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`ea201_diorama`.`cscart_categories`.`usergroup_ids`)) and (`ea201_diorama`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}