Explain design patterns you have implemented

Asks the candidate to enumerate design patterns they have personally implemented in production, explaining the problem context, why the pattern was chosen, and the trade-offs involved. The discussion frequently drills into the Bridge pattern.

Bridge Pattern Deep-Dive

The Bridge pattern decouples an abstraction from its implementation so the two can vary independently.

• Motivation: Avoid a Cartesian explosion of subclasses when there are two orthogonal dimensions of variation (e.g., shapes × rendering engines, devices × remote controls).
• Structure: An Abstraction holds a reference to an Implementor interface. Concrete abstractions and concrete implementors evolve independently.
• vs. Adapter: Bridge is designed up-front; Adapter is a retrofit. Bridge separates concerns proactively.
• vs. Strategy: Strategy varies behavior/algorithm; Bridge varies the implementation platform/backend while keeping a stable abstraction hierarchy.
• Real-world examples: JDBC driver architecture, GUI toolkits (AWT), platform-independent rendering pipelines.

Common Follow-Ups

• Draw the class diagram for the Bridge pattern.
• When would you prefer Bridge over inheritance?
• How does Bridge relate to dependency injection?
• What are the downsides (indirection, added complexity for simple cases)?