Selfish behavior can often lead to suboptimal outcome for all participants, a phenomenon illustrated by classical examples in game theory, such as the prisoner dilemma . Yet, many algorithms, that are originally designed without explicitly considering incentive properties, are later used in settings when participants can act strategically. How good are they in the presence of strategic behavior? We'll will show robust guarantees for performance on a broad range of algorithms in presence of strategic behavior of the participants. Joint work with Paul Duetting and Thomas Kesselheim.