The VCDX Defense Alternatives box included some items that had been discussed during the design phase of the project and others that never were an option in the beginning (due to constraints).
This included most storage protocols around, specific network topologies or just different hardware layouts. All of the options were a possibility but didn’t fit the design requirements/constraints or the selected option fulfilled them better (justification).
Here are some of the boxes from my defense slides:
Many of these had a specific Alternative Design Slide in the slide deck to show the logical diagram if that option would have been selected. Also Pros/Cons and justification were either on the slide or in the note section below.
Others were just a short answer that included pros/cons and justification, and for some a whiteboard diagram idea if asked for it.