Had anyone here done formation.dev? What are your impressions and takeaways?

Hi! Short answer: no. Long answer: we accept iOS Fellows on a case by case basis. If you have several years of experience, we can focus on data structures and algorithms and system design, but not iOS specific expertise. You can use Swift for most of your practice, and Javascript/Python in group sessions. Finally, we have we have a few very senior mentors who are iOS engineers (Uber, Square, etc...) who can do one-off sessions to practice iOS system design interviews. Our most recent iOS Fellow received 5 to 10 (lost track) offers from top-tier FAANG companies, but I think having more iOS training would still help.