Performance & optimization interview questions
Scenario-style prompts with sample answer outlines. Focus is on how you would design and reason in real codebases.
- 01Diagnosing scrolling jankYou're building a feed with complex cells, images, gradients, async content, dynamic text, and scrolling feels janky. Walk me through how you would diagnose and fix it.
- 02Using Instruments effectivelyAn app feels slow, but the cause isn't obvious. How do you use Instruments to narrow it down, and which templates do you usually start with?
- 03Image loading and rendering performanceYour screen shows lots of remote images and scrolling gets slow. How would you optimize loading, decoding, caching, and rendering?
- 04Memory growth and OOMsThe app doesn't obviously leak, but memory rises until the process is killed. How do you track down the cause?
- 05App launch timeCold launch is slower than expected. How do you improve it, and what mistakes do teams make?
- 06Table and collection view performanceA table or collection view gets sluggish as content grows. What mistakes do you look for, and how do you fix them?
