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 (
    70125, 31857, 35900, 36611, 36749, 38348, 
    38923, 68327, 70114, 70115, 70116, 
    70117, 70118, 70119, 70120, 70121, 
    70122, 70123, 70124, 70126, 70127, 
    70128, 70129
  )

Query time 0.00049

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "40.26"
    },
    "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": 23,
          "rows_produced_per_join": 23,
          "filtered": "100.00",
          "index_condition": "(`cscart_db`.`p`.`product_id` in (70125,31857,35900,36611,36749,38348,38923,68327,70114,70115,70116,70117,70118,70119,70120,70121,70122,70123,70124,70126,70127,70128,70129))",
          "cost_info": {
            "read_cost": "13.81",
            "eval_cost": "2.30",
            "prefix_cost": "16.11",
            "data_read_per_join": "368"
          },
          "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": [
            "cscart_db.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 23,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "5.75",
            "eval_cost": "2.30",
            "prefix_cost": "24.16",
            "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": [
            "cscart_db.p.group_id"
          ],
          "rows_examined_per_scan": 2,
          "rows_produced_per_join": 46,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "11.50",
            "eval_cost": "4.60",
            "prefix_cost": "40.26",
            "data_read_per_join": "4K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}