optimized_struct.go

package main

import (
	"fmt"
	"unsafe"
)

type Key struct { // 32 + 12 = 44 bytes
	t    bool   // 1 byte + 7 bytes padding
	id   string // 16 bytes + 12 bytes data for ObjectID values
	hash uint32 // 4 bytes + 4 bytes padding
}

type OptimizedKey struct {
	id   string // 16 bytes + 12 bytes data for ObjectID values
	hash uint32 // 4 bytes
	t    bool   // 1 byte + 1 bytes padding
}

type Sum uint64 // 8 bytes

func main() {
	old := Key{true, "", 0}
	opt := OptimizedKey{"", 0, true}
	fmt.Println(unsafe.Sizeof(old), unsafe.Sizeof(opt))
}