SELECT 
  f.feature_id, 
  f.purpose, 
  p.product_id, 
  p.parent_product_id, 
  g.id, 
  g.code 
FROM 
  cscart_product_variation_group_features AS f 
  INNER JOIN cscart_product_variation_groups AS g ON f.group_id = g.id 
  INNER JOIN cscart_product_variation_group_products AS p ON f.group_id = p.group_id 
WHERE 
  p.product_id IN (
    82071, 82118, 82073, 82038, 149042, 
    82061, 81948, 82009, 82101, 81647, 
    82133, 82103, 81737, 81655, 82104, 
    81704, 81826, 81863, 81741, 81860
  )

Query time 0.00131

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "86.04"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "p",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "product_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 20,
          "rows_produced_per_join": 20,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "24.03",
            "eval_cost": "4.00",
            "prefix_cost": "28.03",
            "data_read_per_join": "320"
          },
          "used_columns": [
            "product_id",
            "parent_product_id",
            "group_id"
          ],
          "attached_condition": "(`webmarco`.`p`.`product_id` in (82071,82118,82073,82038,149042,82061,81948,82009,82101,81647,82133,82103,81737,81655,82104,81704,81826,81863,81741,81860))"
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "id"
          ],
          "key_length": "3",
          "ref": [
            "webmarco.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 20,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "20.00",
            "eval_cost": "4.00",
            "prefix_cost": "52.03",
            "data_read_per_join": "7K"
          },
          "used_columns": [
            "id",
            "code"
          ]
        }
      },
      {
        "table": {
          "table_name": "f",
          "access_type": "ref",
          "possible_keys": [
            "idx_group_id"
          ],
          "key": "idx_group_id",
          "used_key_parts": [
            "group_id"
          ],
          "key_length": "3",
          "ref": [
            "webmarco.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 28,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "28.34",
            "eval_cost": "5.67",
            "prefix_cost": "86.04",
            "data_read_per_join": "2K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}