Recruiter reached out on LinkedIn, quick intro call - background, past projects, why DoorDash. A few high-level iOS questions (UIKit, Core Data), nothing deep. Then got the take-home, took ~5 hours - extend an Xcode project, load & display JSON data. Kept it modular. Tech phone screen with an iOS engineer - mostly take-home discussion, (why you structured things a certain way and trade-offs). Some Swift follow-ups (structs vs. classes, GCD, memory management). Know your take-home inside out. Onsite had 4 rounds - 1st was coding on an existing project, debugging + extending functionality. 2nd was live coding, LC medium-hard, focus on performance & clean code. System design was an iOS architecture problem - scalability, state management, API design. Last was behavioral - teamwork, past challenges, handling conflicts. Key is to be sharp on Swift, system design, debugging. Mocked with ex-DoorDash engineers at Prepfully - helped a lot. Got the offer!

Disadvantages of using the Singleton design pattern.