SELECT 
  feature_id, 
  feature_type 
FROM 
  cscart_product_features 
  INNER JOIN cscart_ult_objects_sharing ON (
    cscart_ult_objects_sharing.share_object_id = cscart_product_features.feature_id 
    AND cscart_ult_objects_sharing.share_company_id = 1 
    AND cscart_ult_objects_sharing.share_object_type = 'product_features'
  ) 
WHERE 
  feature_id IN (3, 6, 4, 16)

Query time 0.00037

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "14.41"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_features",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "feature_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 4,
          "rows_produced_per_join": 4,
          "filtered": "100.00",
          "index_condition": "(`ea201_francemaqu`.`cscart_product_features`.`feature_id` in (3,6,4,16))",
          "cost_info": {
            "read_cost": "8.81",
            "eval_cost": "0.80",
            "prefix_cost": "9.61",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "feature_id",
            "feature_type"
          ]
        }
      },
      {
        "table": {
          "table_name": "cscart_ult_objects_sharing",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "share_object_id",
            "share_company_id",
            "share_object_type"
          ],
          "key_length": "159",
          "ref": [
            "ea201_francemaqu.cscart_product_features.feature_id",
            "const",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 4,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "4.00",
            "eval_cost": "0.80",
            "prefix_cost": "14.41",
            "data_read_per_join": "640"
          },
          "used_columns": [
            "share_company_id",
            "share_object_id",
            "share_object_type"
          ],
          "attached_condition": "(`ea201_francemaqu`.`cscart_ult_objects_sharing`.`share_object_id` = `ea201_francemaqu`.`cscart_product_features`.`feature_id`)"
        }
      }
    ]
  }
}