It's standard iteration process. This is why most of design and development process diagrams are displayed as continuous circle. Nothing has been perfect for fi

It's standard iteration process. This is why most of design and development process diagrams are displayed as continuous circle. Nothing has been perfect for first try. Speed and/or size improvement in next iteration is much better than completely reworking because of: missed or bad requirements understanding, compatibility issues etc. As was already mentioned, you have to have something working. Only this can be improved. Without working code any speed or size optimization is useless.