The devops handbook how to Create World-Class Agility, Reliability, & Security in Technology Organizations By Gene Kim, Jez Humble, Patrick Debois, and John Willis

• 
Identify the system’s constraint.
• 
Decide how to exploit the system’s constraint.
• 
Subordinate everything else to the above decisions.
• 
Elevate the system’s constraint.
• 
If in the previous steps a constraint has been broken, go back to 
step one, but do not allow inertia to cause a system constraint.
In typical DevOps transformations, as we progress from deployment lead 
times measured in months or quarters to lead times measured in minutes, 
the constraint usually follows this progression:
• 
Environment creation: We cannot achieve deployments on- 
demand if we always have to wait weeks or months for production 
or test environments. The countermeasure is to create environ-
ments that are on demand and completely self-serviced, so that 
they are always available when we need them.
• 
Code deployment: We cannot achieve deployments on demand 
if each of our production code deployments take weeks or months 
to perform (i.e., each deployment requires 1,300 manual, error- 
prone steps, involving up to three hundred engineers). The 
countermeasure is to automate our deployments as much as 
possible, with the goal of being completely automated so they 
can be done self-service by any developer.
• 
Test setup and run: We cannot achieve deployments on demand 
if every code deployment requires two weeks to set up our test 
environments and data sets, and another four weeks to manually 
Promo 
- Not 
for 
distribution 
or 
sale

---

Chapter 2 • 23
execute all our regression tests. The countermeasure is to auto-
mate our tests so we can execute deployments safely and to 
parallelize them so the test rate can keep up with our code devel-
opment rate.