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 (
    315, 316, 199, 198, 201, 192, 195, 191, 
    196, 197, 200, 202, 203, 204, 194
  )

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "83.30"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "p",
          "access_type": "ALL",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "rows_examined_per_scan": 106,
          "rows_produced_per_join": 14,
          "filtered": "14.15",
          "cost_info": {
            "read_cost": "20.56",
            "eval_cost": "3.00",
            "prefix_cost": "23.56",
            "data_read_per_join": "239"
          },
          "used_columns": [
            "product_id",
            "parent_product_id",
            "group_id"
          ],
          "attached_condition": "(`atulecarter_atul_demo2`.`p`.`product_id` in (315,316,199,198,201,192,195,191,196,197,200,202,203,204,194))"
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "id"
          ],
          "key_length": "3",
          "ref": [
            "atulecarter_atul_demo2.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 14,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "15.00",
            "eval_cost": "3.00",
            "prefix_cost": "41.56",
            "data_read_per_join": "5K"
          },
          "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": [
            "atulecarter_atul_demo2.p.group_id"
          ],
          "rows_examined_per_scan": 3,
          "rows_produced_per_join": 51,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "31.50",
            "eval_cost": "10.24",
            "prefix_cost": "83.30",
            "data_read_per_join": "5K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}