Software Engineering at Google

earlier we find a problem, the cheaper it is to fix it

Bus factor (noun): the number of people that need to get hit by a bus before your project is completely doomed.

We see three critical differences between programming and software engineering: time, scale, and the trade-offs at play. On a software engineering project, engineers need to be more concerned with the passage of time and the eventual need for change. In a software engineering organization, we need to be more concerned about scale and efficiency, both for the software we produce as well as for the organization that is producing it. Finally, as software engineers, we are asked to make more complex decisions with higher-stakes outcomes, often based on imprecise estimates of time and growth.

How an organization will need to adapt as it evolves

Trade-offs and Costs
How an organization makes decisions, based on the lessons of Time and Change and Scale and Growth

Time and Change
How code will need to adapt over the length of its life

Scale and Growth

With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your system will be depended on by somebody.