21 patterns, written to be argued with
Not another patterns glossary. Each entry tells you when the pattern is the wrong choice, walks through working code, and links a live demo — so you can judge it before you bet a quarter on it.
One slow dependency should not be able to consume every thread you have. Bulkheads partition resources so a failure stays inside its compartment — and the hard part is sizing them, not building them.
You cannot atomically write to your database and publish to a broker. The Outbox pattern makes the message part of the transaction — and the trap is that at-least-once delivery is the ceiling, not a bug.
Protecting a service from too much traffic sounds like arithmetic. It is really a question about fairness, and the algorithm you pick decides who gets refused when the answer is no.
Replacing a legacy system by rewriting it has a poor record. The Strangler Fig replaces it incrementally behind a facade — and the reason it works is organisational as much as technical.
Ship a new version to a small slice of real traffic, compare it against a baseline on live signals, and promote or roll back on evidence — progressive delivery where the release decision is made by data, not by nerve.
The default data-access pattern as a deliberate choice, not an absence of one: what one shared model buys you, the four failure modes that eventually break it, and the signals you have outgrown it.