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 (
    5823, 12916, 12921, 12956, 12958, 13014, 
    13028, 13040, 13052, 12960, 12974, 
    12988, 13000, 12926, 12942, 12876, 
    12896, 12900, 12909
  )

Query time 0.00125

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "73.01"
    },
    "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": 21,
          "rows_produced_per_join": 21,
          "filtered": "100.00",
          "index_condition": "(`test2_gaseus`.`p`.`product_id` in (5823,12916,12921,12956,12958,13014,13028,13040,13052,12960,12974,12988,13000,12926,12942,12876,12896,12900,12909))",
          "cost_info": {
            "read_cost": "12.11",
            "eval_cost": "2.10",
            "prefix_cost": "14.21",
            "data_read_per_join": "336"
          },
          "used_columns": [
            "product_id",
            "parent_product_id",
            "group_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "id"
          ],
          "key_length": "3",
          "ref": [
            "test2_gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 21,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "5.25",
            "eval_cost": "2.10",
            "prefix_cost": "21.56",
            "data_read_per_join": "8K"
          },
          "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": [
            "test2_gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 7,
          "rows_produced_per_join": 147,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "36.75",
            "eval_cost": "14.70",
            "prefix_cost": "73.01",
            "data_read_per_join": "14K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}