Meta Software Engineer (IOS) interview questions

I was referred by an Instagram engineer. A few hours later I was contacted by a recruiter asking me for times that I could schedule a technical phone screen. I ended up doing the call a week after I was contacted. The question wasn't hard, but I wasn't familiar with it and it took up the whole call. They let me know a few days later that they won't be moving forward but encouraged me to apply again. The whole process was super nice and everyone that I talked to was very friendly. I'll definitely be applying next year.