What the round is like
In recent reports, the design round was split: about 30 minutes of system design and 30 minutes of Leadership Principles. That's not much time, so get your requirements and rough numbers down fast and save time for the follow-ups.
What people have been asked
These come up in candidates' own write-ups of their interviews, and most of them are things Amazon actually builds. We wrote the example prompts ourselves, so the wording you get will be different.
Design a social media news feed
Users post text, images and video, see posts from people they follow, and like and view posts with live counts.
The feed has to load almost instantly, and one celebrity post can get millions of likes in seconds without becoming a bottleneck.
How it might be asked
Design a feed like Facebook's where millions of users can post text, images and videos and see posts from the people they follow. Like and view counts should update in real time, and the feed should load almost instantly, even for someone who's just cleared their cache.
Key concepts to know
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Design an online checkout
Take a customer from their cart to a confirmed order: hold the stock, take the payment, and confirm it.
You can never charge someone twice or sell stock you don't have, even when the payment provider times out.
How it might be asked
Design the checkout for an online store like Amazon. A customer reviews their cart, pays, and gets an order confirmation. We must never charge anyone twice, and we can't sell more of an item than we have.
Key concepts to know
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Design a music streaming app
Let millions of people search for songs, build playlists, save a library and start playback almost instantly.
The songs themselves are big files that need to start playing fast, while search and playlists are small, busy data.
How it might be asked
Design a music streaming service like Spotify. Users can search songs, artists and albums, make playlists and like songs. Playback should start almost immediately for millions of listeners at once, and the service should basically never be down.
Key concepts to know
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Design product recommendations
Show each shopper products they're likely to want, based on what they and similar shoppers did.
Separate the heavy work that can happen in the background from the quick lookup when a page loads.
How it might be asked
Design the 'customers who bought this also bought' and 'recommended for you' sections. They should reflect recent activity and load quickly on every product page.
Key concepts to know
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What's really being tested
| Topic | What you're being asked, basically |
|---|---|
| Read-heavy pages | What can you work out ahead of time so pages load instantly? |
| Hot items | What happens when one post or product gets a flood of traffic? |
| Correctness | Where can you never be wrong, like charges and stock? |
| Async work | What can happen after the response, using a queue? |
How to work through a question
- Figure out what you're building. Who's using it, what does it need to do, and what can you ignore?
- Do some rough math. How many requests, how much data, more reads or more writes? Those answers decide a lot.
- Walk through one request. Draw the simplest thing that works before you add anything fancy.
- Pick storage last. Once you know what gets read, how often and how fresh it has to be, the choice gets a lot easier.
- Then try to break it. What happens in a traffic spike? What if a server dies?
Key concepts to know
If you're rusty on any of these, start here.
- Caching strategiesMake reads faster, and figure out what to do when data changes.
- Message queues and event streamsKeep services from depending on each other, and handle traffic spikes.
- Idempotency and retriesMake sure a retried request doesn't happen twice.
- Relational vs non-relational databasesPick a database based on how you'll actually use it.
- Sharding and consistent hashingSplit data across machines and keep it balanced.
- Consistency and the CAP theoremWhat happens when copies of your data can't agree.
- Stream processing and windowingCount things in data that never stops coming in.
- Real-time deliveryPush updates to users the moment they happen, with WebSockets and friends.
- Blob storage and CDNsStore big files cheaply and serve them from close to your users.
- Search and inverted indexesFind text fast, rank what comes back, and keep the index fresh.
Sources
We pulled this together from candidates' own write-ups of their interviews. They don't always agree, and things change over time.
- LeetCode Discuss: SDE-2 interview experience (2026, Prime Video)
- LeetCode Discuss: SDE online assessment with an AI-assisted task (2026)
- Taro: SDE II, Austin (Oct 2025)
- Taro: SDE II, Seattle (Oct 2025)
- Taro: SDE II, New York (Jun 2025)
- Taro: SDE 2, Bengaluru (Feb 2025)
- Blind: asked to design Amazon Locker
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