Runtime performance is essential for real time games, the faster a game can run the more features designers can put into the game to accomplish their vision. A popular architecture for video games is the Entity Component System architecture aimed to improve both object composition and performance. There are many tests for how this architecture performs under its optimal linear execution. This thesis presents a performance comparison of how several popular open-source Entity Component System libraries perform when fetching data from other entities during iteration. An object-oriented test is also done to compare against and verify if the known drawbacks of object-orientation can still be seen within these test cases. Our results show that doing a random lookup during iteration can cause magnitudes worse performance for Entity Component Systems.