What are some real world applications for genetic algorithms? What are some real world problems that have been solved using a genetic algorithm?   What is the problem?  What is the fitness test used to solve this problem?
The optimizer in relational databases. Examples are PostgreSQL and H2; other databases most likely also use a genetic algorithm. The problem is: selecting the best query plan (the one with the lowest estimated cost) is NP-hard. The fitness test is the estimated cost.