What You'll Learn
Reason Before You Architect
Every module and every System Design Case File walks the same eleven steps, so the reasoning is repeatable under any prompt \u2014 from a URL shortener to a payment system.
Problem Space
Name the system being constructed and the world it must operate in before any structure is chosen.
Requirements
Separate what the system must do from how well it must do it — the contract every decision must satisfy.
Constraints
List the hard limits that cannot be traded away. A constraint that forbids nothing constrains nothing.
Actors
Name the users, services, and external systems that define the surfaces and boundaries of the system.
State
Identify the data, its lifetime, its volume, and its ownership — the part of a system that makes a decision irreversible.
Invariants
State the guarantees the system cannot violate. The invariant is the proof the design preserves.
Failure Modes
Enumerate the ways components, networks, and processes can fail. A system is designed by its failure modes, not its happy path.
Architecture Options
Generate the lawful candidates — monolith, modular services, event-driven — each a hypothesis to be tested.
Tradeoffs
Weigh every candidate against the constraints and record what each choice gains and forfeits.
Decision
Select the architecture justified by the evidence — a justified conclusion, not a preference.
Proof
Connect every constraint and invariant to a concrete verification: a load model, a failure drill, a capacity calculation.
Table of Contents
Four Parts, One Method
From the system contract through state, invariants, and failure modes, to architecture justified by proof \u2014 and the ten case files that make the method repeatable.
From the Book
How the Method Reads
A System Is Designed by Its Failure Modes
The happy path is a story the system tells once. The failure modes are the conditions it must survive forever. Naming what can fail, and what each failure does to the invariants, is where architecture starts.
The Decision Is the Proof
An architecture choice is not a preference. It is the candidate that best satisfies the constraints under the recorded tradeoffs — and it must be re-openable when the evidence changes.
See the Framework
Start With the Videos
What Is the Correct Code Framework?
Why CCF starts with intent, structure, and proof before code.
Watch on the video libraryCorrect Code Philosophy
The reasoning-first philosophy behind the framework.
Watch on the video librarySome videos require membership access. Visit the video library to see what's unlocked for your plan.
Who It's For
Book Six is for Pro members ready to reason about systems
Where It Fits
The Fourth Stage of the Curriculum Ladder
Unlock the Systems Book
CCF System Design is included with CCF Pro, the advanced plan for engineers who want the full Correct Code Framework library and the System Design curriculum.