SELECT 
  f.feature_id, 
  fd.description, 
  f.position 
FROM 
  cscart_product_features f 
  LEFT JOIN cscart_product_features_descriptions fd ON f.feature_id = fd.feature_id 
  AND fd.lang_code = 'en' 
WHERE 
  1 
  AND f.feature_id IN ('345', '1392')

Query time 0.00063

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.11"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "f",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "feature_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 2,
          "rows_produced_per_join": 2,
          "filtered": "100.00",
          "index_condition": "(`chocoramo`.`f`.`feature_id` in ('345','1392'))",
          "cost_info": {
            "read_cost": "1.21",
            "eval_cost": "0.20",
            "prefix_cost": "1.41",
            "data_read_per_join": "880"
          },
          "used_columns": [
            "feature_id",
            "position"
          ]
        }
      },
      {
        "table": {
          "table_name": "fd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "feature_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "chocoramo.f.feature_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 2,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.50",
            "eval_cost": "0.20",
            "prefix_cost": "2.11",
            "data_read_per_join": "4K"
          },
          "used_columns": [
            "feature_id",
            "description",
            "lang_code"
          ]
        }
      }
    ]
  }
}