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 (
    20482, 20543, 20496, 20495, 20492, 20489, 
    20498, 20497, 20540, 20541, 20542, 
    20491, 20422, 20493, 20480, 20483, 
    20467, 20477, 20511, 20494, 20499, 
    20234, 20272, 20479
  )

Query time 0.00138

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "f",
      "access_type": "ALL",
      "possible_keys": ["idx_group_id"],
      "rows": 6,
      "filtered": 100
    },
    "table": {
      "table_name": "g",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["id"],
      "ref": ["admin_test.f.group_id"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "p",
      "access_type": "ALL",
      "possible_keys": ["PRIMARY", "idx_group_id"],
      "rows": 15,
      "filtered": 80,
      "attached_condition": "p.group_id = f.group_id and p.product_id in (20482,20543,20496,20495,20492,20489,20498,20497,20540,20541,20542,20491,20422,20493,20480,20483,20467,20477,20511,20494,20499,20234,20272,20479)"
    }
  }
}