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 (
    3400, 5691, 5687, 3733, 3552, 2805, 3232, 
    4915, 6025, 3149, 3416, 3157, 3589, 
    5791, 3845, 3150, 2481, 3822, 4976, 
    3115, 3740, 3123, 2228, 3743
  )

Query time 0.00214

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "37.06"
    },
    "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": 27,
          "rows_produced_per_join": 27,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`p`.`product_id` in (3400,5691,5687,3733,3552,2805,3232,4915,6025,3149,3416,3157,3589,5791,3845,3150,2481,3822,4976,3115,3740,3123,2228,3743))",
          "cost_info": {
            "read_cost": "15.46",
            "eval_cost": "2.70",
            "prefix_cost": "18.16",
            "data_read_per_join": "432"
          },
          "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": [
            "softwarepirmam_hewadelivard_cscart_4.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 27,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "6.75",
            "eval_cost": "2.70",
            "prefix_cost": "27.61",
            "data_read_per_join": "10K"
          },
          "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": [
            "softwarepirmam_hewadelivard_cscart_4.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 27,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "6.75",
            "eval_cost": "2.70",
            "prefix_cost": "37.06",
            "data_read_per_join": "2K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}