Which design patterns show up most often in everyday software development?

A useful way to think about patterns is as vocabulary for recurring solutions. A Facade hides a complicated API, Strategy represents interchangeable ways to perform an operation, Observer lets other components react to changes, and a Factory centralizes complicated construction. Learn what problems they address, then recognize them in real code instead of trying to use every pattern deliberately.

There isn’t really a universal ranking of patterns. They usually emerge from the problems a project has, rather than being goals you should force into the design. If you program to interfaces instead of concrete implementations, you’ll often end up using ideas related to dependency injection, factories, strategies, and other patterns naturally.

In embedded firmware, Singleton, State, Factory, Builder, and Command patterns come up fairly often, especially in large or long-lived codebases. Factories can still be useful when object creation depends on configuration, hardware, or runtime conditions, even if a project avoids formal pattern-heavy architecture.

Be careful with treating patterns as recipes. Strategy can be useful, but it can also make a straightforward design harder to follow if every small variation becomes a separate class. Likewise, a Singleton is usually best avoided in favor of creating one shared instance and passing it where needed. A true Singleton is mainly justified when multiple instances would be incorrect for the entire process, such as managing a genuinely unique resource.

Factories, Strategy, and Observer tend to appear in a lot of different kinds of applications. Facade, Proxy, and Iterator are also common. Some patterns, especially Iterator, are built into modern languages and libraries so thoroughly that developers use them without thinking of them by name.