System design interview practice
Design one system end to end on a shared whiteboard. Vera reads what you draw, asks about it, and changes one thing at a time to see what breaks. You leave with a report that quotes your reasoning.
- 45 to 50 min
- One, end to end
- Up to two small nudges
- Shared whiteboard Vera can read
How the round runs
- 01
Requirements and scope
Vera states the problem in a sentence or two and invites questions. Pin down what the system must do, the scale and your assumptions before any boxes.
- 02
High-level design
Walk through the main flow end to end. Expect questions about the API, the data model and why you picked that storage.
- 03
Deep dive
Vera picks the riskiest or least explained part and asks how it actually works, not what it is called.
- 04
Scale and failures
One twist at a time: load grows ten times, a node fails mid-request, one key gets hot. What breaks first, and what does the user see?
- 05
Wrap-up
Name the weakest parts of your design, how you would monitor and roll it out, and what version two would add.
What the report scores
Each skill gets a score from 1 to 5 against the bar for your level, with the quotes it is based on and the time you said them. The report ends with one thing to fix next.
- Requirements and scoping
- Structure and driving
- API and data model
- Architecture
- Depth
- Trade-offs
- Scale and failure handling
- Communication
At lead level, also: Operability and cost, Scope and influence.
How the real round works
A system design interview usually lasts 45 to 60 minutes and moves through the same steps: clarify the requirements, sketch the API and data, draw a simple design that works end to end, go deep on two or three parts, then close with bottlenecks and improvements. The most common way to fail, according to the prep guides we read, is running out of time without one coherent design.
How system design interviews work: structure, signals and common mistakesRegular and lead level
- Regular
- Vera guides gently. Jump straight to boxes and you are asked for requirements and scale first; stall and you get a small prompt about the next area.
- Lead
- Vera does not structure it for you. You drive the agenda, pick the risky parts and cover cost, operations and team impact. Name a technology and you will be asked how it works here.
Length: 45 minutes at regular, 50 at lead.
In each role
- Software Engineering
System design. Design a large-scale service end to end, with trade-offs.
- Data Science
Metrics & experimentation design. Design an experiment, metric framework or analytics pipeline.
- Machine Learning
ML system design. Design a production ML system: data, training, serving, monitoring.
- Quant Developer (C++)
Low-latency system design. Design a matching engine, feed handler or low-latency pipeline.
See the feedback before you start
Full reports from the real report pipeline, for a fictional student and a scripted interview.
Questions
Do I draw, or just talk?
Both. You draw boxes and arrows on a shared whiteboard while you talk, and Vera reads what you add and asks about it, the way an interviewer looks over your shoulder.
What are the twists?
In the scale and failures stage Vera changes one thing at a time, for example ten times the load, a node failing mid-request or a hot key, and asks what breaks first and what the user sees.
Is there a system design round for data science, ML and quant?
Yes. Data science designs an experiment, metric framework or analytics pipeline. Machine learning designs a production ML system. Quant designs a matching engine, feed handler or low-latency pipeline.
Will Vera tell me the right answer?
No. If you ask what Vera thinks, you get a short, balanced view of what an option buys and costs, never a verdict. The report afterwards shows what was strong and what to fix.