Every chapter ends with a Compression Block. It looks like this:
Concept: The recall trigger
Thread: Which of the 12 threads this connects to
Core Idea: One sentence
Tradeoff: The named architecture tradeoff this creates (from F4)
Failure Mode: What breaks when this is misapplied (from F3)
Signal: When you should be thinking about this
Maps to: Which books in the series go deep on this
The Compression Block is a flashcard. When revising, cover the right column and try to produce each field from the concept name alone. If you cannot, read the field, then look away and repeat it. Do not move on until you can produce the field from memory.
This is active recall, not passive review. The difference in retention is approximately five to one.