After an initial phone call with the HR person I got several code challenges to resolve without a time limit. I resolved them using the best approach for their requirements and sent them back with extensive documentation about the problem, the solution and the strategy chosen to resolve it. After few days the HR person told me the technical manager didn't want to continue with my application, and when asked for feedback about my code implementation she said she will ask the manager and get back to me. But she never did. I don't think is a good recruiting practice to drop technical applications after a code challenge without providing at least a very basic feedback. Code challenges take several hours to research, code, test and document, and you would expect at least the courtesy of the reviewer to follow up with you.