Closing Comparison

Both systems are distributed. Both use the same toolkit. But their architecture goals are different.

• Blockchain: maximize liveness in a hostile network (gossip, validation, eventual convergence).
• Order book: maximize determinism and strict ordering (single sequencer, strict price-time priority).

The same primitives still carry both designs:

• JoinSet for lifecycle ownership
• framed transport for protocol correctness
• Tower middleware for resilience edges
• tracing for reconstructing what happened

That is the capstone takeaway of this book:

Do not memorize one architecture. Reuse strong building blocks, then optimize for domain invariants.