What the round is like
The design round is about 45 minutes. Product and full-stack roles often get product architecture instead of system design. It focuses on entities, APIs, pagination and the user-facing flow rather than infrastructure.
What people have been asked
These come up in candidates' own write-ups of their interviews. We wrote the example prompts ourselves, so the wording you get will be different.
Show each listener their top 10 songs
Every listener sees their 10 most-played songs over the last 4 weeks, kept up to date as they listen. The same top-k pattern also shows up as trending hashtags.
It's a top-k problem per user, over a sliding time window, for a huge number of users.
How it might be asked
Design a feature for a music streaming service that shows every listener their 10 most-played songs over the last 4 weeks, updated as they listen.
Key concepts to know
Try this Interview
Build a coding contest platform
Came up as a product architecture round. Thousands of people join timed contests, submit code that runs against tests, and watch a live leaderboard.
Running untrusted code safely, a huge rush at the start and end, and keeping many contests going at once.
How it might be asked
Design a coding contest platform like LeetCode's weekly contest. Thousands of people join a timed contest, submit code that's run against tests, and see a live leaderboard. Several contests can run at the same time.
Key concepts to know
Try this Interview
Design a food delivery app
Customers order from restaurants, couriers pick up and deliver, and everyone sees the order's status as it moves along.
The order goes through a lot of states with three different people involved, and the customer expects live updates the whole way.
How it might be asked
Design a food delivery app like DoorDash. Customers browse restaurants and place orders, restaurants accept them, a courier is assigned, and the customer can follow the order until it arrives.
Key concepts to know
Try this Interview
Design a news feed
Several 2025-26 candidates got a news feed or Instagram-style feed, often in the product architecture round.
Decide whether to build feeds ahead of time or when someone opens the app, and what to do about celebrities. Product architecture versions dig into APIs, pagination and post types more than infrastructure.
How it might be asked
Design the news feed. People see recent posts from friends and pages they follow, ranked so the most interesting are near the top, and the feed should load quickly.
Key concepts to know
Try this Interview
What's really being tested
| Topic | What you're being asked, basically |
|---|---|
| Fan-out | When one thing happens, how many people need to know, and how fast? |
| Ranking | What do you work out ahead of time, and what at read time? |
| Caching | What do you cache, and how do you keep it fresh? |
| Scale | What changes when it's billions of users instead of millions? |
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.
- Stream processing and windowingCount things in data that never stops coming in.
- Message queues and event streamsKeep services from depending on each other, and handle traffic spikes.
- Sharding and consistent hashingSplit data across machines and keep it balanced.
- Heaps and priority queuesAlways have the smallest or largest item ready.
- Geospatial indexingFind what's nearby with map grids like geohashes and H3.
- Rate limitingStop too much traffic with token buckets and sliding windows.
- 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.
- 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.
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: Meta E5 offer, Menlo Park (2024)
- LeetCode Discuss: Meta E4 onsite passed (Feb 2025)
- LeetCode Discuss: Meta E5 onsite, Bangalore (2025)
- LeetCode Discuss: Meta product E4, news feed design (2025)
- LeetCode Discuss: Meta full loop with AI-enabled round (Oct 2025)
- LeetCode Discuss: Meta SDE2, AI-enabled round and product architecture (Nov 2025)
- LeetCode Discuss: Meta E4 US offer, DoorDash design (Dec 2025)
- LeetCode Discuss: Meta E4 Bangalore, AI coding and product architecture (2026)
Practice Loop is an independent practice tool and isn't affiliated with or endorsed by Meta.