Systems
Boundaries you can operate
A good engineer should be able to run your system without asking the person who built it. That starts with knowing what owns each piece of state.
By David Discua · Last updated
Most outages aren't caused by missing features. They're caused by missing boundaries: two services sharing a database, a job writing through a side door, a model making a decision nobody can override.
Write down what owns state, what can fail on its own, and which interfaces can change. Those three answers prevent more incidents than any new framework.
Keep the map short enough to remember. If it only exists in a slide deck, it isn't really the architecture.