Many roles at Fannie Mae require you to think and act quickly in a fast-paced environment. As a result, you will likely deal with colleagues and clients who are stressed out, overwhelmed, or working under tight deadlines. Your interviewer wants to know that you will be able to work effectively in that kind of environment. Discuss a time when you've thrived in a high-pressure and fast-paced environment like this in the past, highlighting the personality traits that have contributed to your success in these types of situations.
Changes in interest rates, world events, and demographics--as well as mismatches between supply and demand--are all external factors that have the potential to add to stress levels among colleagues and clients. Demonstrate that you can handle volatility with these factors without crumbling under pressure.