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 (
    2037, 2038, 5668, 5669, 5670, 5671, 5672, 
    5673, 5674, 5675, 5676, 5677, 5678, 
    5679, 5680, 5681, 5682, 5683, 5684, 
    5685, 5686, 5687, 5688, 5689
  )

Query time 0.00047

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "50.41"
    },
    "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": 24,
          "rows_produced_per_join": 24,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`p`.`product_id` in (2037,2038,5668,5669,5670,5671,5672,5673,5674,5675,5676,5677,5678,5679,5680,5681,5682,5683,5684,5685,5686,5687,5688,5689))",
          "cost_info": {
            "read_cost": "14.41",
            "eval_cost": "2.40",
            "prefix_cost": "16.81",
            "data_read_per_join": "384"
          },
          "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": [
            "gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 24,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "6.00",
            "eval_cost": "2.40",
            "prefix_cost": "25.21",
            "data_read_per_join": "9K"
          },
          "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": [
            "gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 3,
          "rows_produced_per_join": 72,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "18.00",
            "eval_cost": "7.20",
            "prefix_cost": "50.41",
            "data_read_per_join": "7K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}