A product page feels slow to load on mobile. How would you find out why, and what would you try first?

What the interviewer is looking for

• This question tests web performance. Measures with real tools such as browser profilers and Core Web Vitals including Interaction to Next Paint, and names concrete fixes like code splitting, image optimisation and reducing re-renders.
• Strong answers: Measuring with browser tools and real user metrics, looking at bundle size, images, render-blocking resources and slow requests, and prioritising fixes by impact.
• Likely follow-up: How would you stop performance from slipping again after you fix it?

Another way it may be asked: Customers complain the product page takes ages on their phones. Walk me through how you'd investigate and fix it.

A structure to follow: Answer, explain, example, limits

1. Step 1

   Answer

   Give your direct answer in the first sentence so the interviewer knows where you are going.

2. Step 2

   Explain

   Say how it works or why you would do it that way, in plain words before jargon.

3. Step 3

   Example

   Anchor it in something you have actually done or seen, with the detail that shows hands-on experience.

4. Step 4

   Limits

   Say when your approach would not be the right one. It shows judgement.

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

• Reciting a definition without showing you have applied it.
• Using terms you cannot explain if asked a level deeper.
• Claiming experience beyond what you can discuss in detail.

How to practise it

Say the answer in 90 seconds, then answer the follow-up as if it were a new question.

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