How would you build a scrolling list of thousands of items so it stays smooth on an older phone?

What the interviewer is looking for

• This question tests performance & battery. Uses platform profilers, keeps the main thread free, and names concrete fixes for jank, memory and battery drain.
• Strong answers: Recycled or lazy list views, image downsizing and caching, moving work off the main thread, pagination, and profiling to confirm.
• Likely follow-up: Which tool would you use to prove where the stutter comes from?

Another way it may be asked: Your feed stutters when users scroll quickly on a three-year-old phone. How do you make it smooth?

A structure to follow: Frame, structure, analyse, recommend

1. Step 1

   Frame

   Restate the goal and ask what success is and what the constraints are.

2. Step 2

   Structure

   Split the problem into a few separate parts you can check one by one, and say what you will look at first and why.

3. Step 3

   Analyse

   Reason with the information you have, state your assumptions out loud, and say what data would change your mind.

4. Step 4

   Recommend

   Give a clear recommendation, the main risk, and the first step you would take.

This is guidance on shape, not a script. Use your own real experience and facts; never invent details to fill a gap. See the STAR guide and answer frameworks.

Common slips

• Listing ideas without choosing between them.
• Hiding assumptions instead of stating them.
• Finishing without a recommendation.

How to practise it

Answer in four spoken parts, one per step, then check you ended on a recommendation.

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