SELECT 
  products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      products_categories.link_type = "M", 
      CONCAT(
        products_categories.category_id, 
        "M"
      ), 
      products_categories.category_id
    )
  ) AS category_ids, 
  product_position_source.position AS position 
FROM 
  products_categories 
  INNER JOIN categories ON categories.category_id = products_categories.category_id 
  AND categories.storefront_id IN (0, 1) 
  AND (
    categories.usergroup_ids = '' 
    OR FIND_IN_SET(0, categories.usergroup_ids) 
    OR FIND_IN_SET(1, categories.usergroup_ids)
  ) 
  AND categories.status IN ('A', 'H') 
  LEFT JOIN products_categories AS product_position_source ON products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 1949 
WHERE 
  products_categories.product_id IN (
    65903, 64064, 64129, 65904, 72762, 65926, 
    63724, 63999, 84007, 74938, 74818, 
    143637, 63457, 65957, 78868, 72822, 
    76710, 83871, 78844, 74942, 72771, 
    64196, 78848, 63460
  ) 
GROUP BY 
  products_categories.product_id

Query time 0.00236

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "74.12"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "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": 82,
            "rows_produced_per_join": 82,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "8.52",
              "eval_cost": "8.20",
              "prefix_cost": "16.72",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`goimagine`.`products_categories`.`product_id` in (65903,64064,64129,65904,72762,65926,63724,63999,84007,74938,74818,143637,63457,65957,78868,72822,76710,83871,78844,74942,72771,64196,78848,63460))"
          }
        },
        {
          "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",
              "goimagine.products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 82,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "20.50",
              "eval_cost": "8.20",
              "prefix_cost": "45.42",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "table": {
            "table_name": "categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "goimagine.products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 4,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "20.50",
              "eval_cost": "0.41",
              "prefix_cost": "74.12",
              "data_read_per_join": "10K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`goimagine`.`categories`.`storefront_id` in (0,1)) and ((`goimagine`.`categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`goimagine`.`categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`goimagine`.`categories`.`usergroup_ids`))) and (`goimagine`.`categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}