A system design mock interview on a whiteboard she can see.
In this system design mock interview you sketch while you talk. Remy sees the boxes and arrows on your whiteboard, asks about scale and failure, and pushes on the trade-off you skipped — for 45 minutes, like the real round.
What a system design interview tests
Scoping the problem
Asking who uses it, how much traffic, and what matters most before drawing anything.
A design you can defend
Clear components and data flow, with a reason for each choice you can say in one sentence.
Scale and failure
What breaks at ten times the load, what happens when a dependency goes down, and how you would notice.
Trade-offs
Consistency versus latency, push versus pull, cost versus simplicity — named, not avoided.
She sees the board and asks about the parts that break.
She watches the board
Draw the client, the gateway, the cache. Her questions point at the box you just added.
She pushes on what you skipped
"What happens to the counter if Redis restarts mid-window?" — the follow-up that separates a sketch from a design.
One or two questions
A 45 minute round holds one or two design questions, so there is time to go deep.
10 system design questions you can practise
Each one with what a strong answer covers: system design interview questions.
System design
10 questionsDesign a distributed rate limiter
Design a rate limiter for a public API used by many clients.
Scope: Cover the algorithm, where the state lives, limits per client, and what happens when the limiter itself fails.
Standardrate limitingdistributed systemsreliabilityDesign a URL shortener
Design a service that turns long URLs into short links and redirects visitors.
Scope: Cover id generation, read-heavy traffic, caching, and analytics.
Warm-upurl shortenerhashingcachingDesign a social news feed
Design a home feed that shows posts from the people a user follows.
Scope: Cover fan-out, ranking, freshness, and how you handle very popular accounts.
Hardnews feedfan outrankingDesign a real-time chat system
Design one-to-one and group chat with delivery receipts and history.
Scope: Cover connection management, ordering, offline delivery, and message storage.
HardchatwebsocketsorderingDesign a unique id generator
Design a service that issues globally unique ids at high volume.
Scope: Cover coordination, clock behavior, ordering, and how ids stay sortable.
Standardunique idssnowflakeclock skewDesign a notification service
Design a service that sends push, email, and SMS notifications to a large user base.
Scope: Cover the pipeline from event to delivery, retries, deduplication, and user preferences.
Standardnotificationsqueuesfan outDesign search autocomplete
Design typeahead suggestions for a search box that serves millions of users.
Scope: Cover the data structure, how suggestions are ranked, freshness, and the read path.
StandardsearchtriecachingDesign a distributed task scheduler
Design a system that runs scheduled and recurring jobs across a fleet of workers.
Scope: Cover scheduling, retries, exactly-once effects, and what happens when a worker dies mid-job.
Standardtask schedulingqueuesidempotencyDesign a file storage and sync service
Design a cloud drive that stores user files and syncs them across devices.
Scope: Cover chunking, deduplication, consistency, conflict handling, and multi-region durability.
Hardfile storagededuplicationconsistencyDesign a live video streaming platform
Design live streaming where creators broadcast to many viewers.
Scope: Cover ingest, transcoding, delivery, latency targets, and what happens when a stream goes viral.
Hardvideostreamingcdn
Your own words, and what to say next time.
Say the trade-off before you start coding.
“I'll just use a hash map and sort it, it's probably fine.”11:40 · right before you started typing
“A heap keeps this at n log k. Sorting everything is simpler — I'll start there and say why it's fine for this input.”
About the system design round
Do I need to know a specific cloud provider?
No. Name generic building blocks such as a load balancer, a queue or a cache, and explain why you need them.
Is there a whiteboard, or do I just talk?
There is a whiteboard in the round. Remy reads what you draw, so a clear diagram makes the conversation easier.
Which system design questions are in the library?
Rate limiters, URL shorteners, feeds, chat, notifications, schedulers, file storage and more. The full list is on the system design interview questions page.
More ways to practise
Try a system design round with Remy.
Your first two practices are free. No card needed.
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