I have extensive experience with both Unity and Unreal Engine. I have used Unity for several 2D and 3D projects, utilizing C# for scripting. With Unreal Engine, I have worked on complex 3D games using both Blueprints and C++. I am comfortable with their respective workflows and optimization techniques.

I approach debugging by first trying to reproduce the issue consistently. Once identified, I use logging to trace the problem's source, and debugging tools within the engine to inspect variable states and game environments. Thorough commenting and modular coding also help in isolating problems efficiently.

Optimization is critical in game development, and I focus on both performance and resource management. Techniques I use include efficient memory management, reducing draw calls, optimizing assets, and utilizing Level of Detail (LOD). Profiling tools help analyze performance bottlenecks, and I apply necessary optimizations based on their feedback.

Object pooling is a design pattern used to manage the reuse of objects in a game, reducing the overhead of object creation and garbage collection. It is particularly useful for objects that are frequently created and destroyed, like bullets or enemies in a game. This approach helps maintain performance stability and reduces lag spikes.

Collaboration is vital in game development as it involves multiple disciplines like art, design, and programming. I ensure effective teamwork by maintaining clear communication, using collaboration tools like version control (Git), participating in regular meetings, and giving and receiving constructive feedback. Establishing shared goals also helps in aligning the team's efforts.

One challenging problem was optimizing the AI pathfinding algorithm in a large, open-world game. The initial implementation was causing significant frame rate drops. To solve this, I implemented a hierarchical pathfinding approach combined with a grid-based system. This reduced the complexity of the calculations required and improved performance considerably.