Daily system design calibration
for Senior engineers.
Read a high-stakes architecture scenario over coffee. Think through your tradeoffs, then instantly see the precise breakdown of flawed, Senior, and Principal-level responses. No fluff, just daily signal training.
First full scenario free. Upgrade anytime.
For senior backend engineers who can build the system but want to nail the Staff & Principal interview.
The difference isn't knowledge.
It's judgment.
Most resources explain how systems work. Principal-level evaluation probes how you think—the quality of your tradeoffs under real constraints.
“I'd use Kafka here for the messaging queue because it scales well and is standard.”
“Given the strict ordering requirement but low throughput (100 TPS), Kafka adds unnecessary operational complexity. A simpler Postgres-backed job queue suffices for v1, minimizing maintenance overhead.”
No “One Right Answer”
Navigate ambiguity, articulate assumptions, and defend engineering judgment when tradeoffs are unclear.
Production Reality
Reason about failure modes, scalability limits, and performance under constraints that textbooks skip.
Four steps. 30 minutes. Every day.
No typing, no gamification. Pure calibration against the Principal bar.
Read the Scenario
A realistic system design problem with production constraints, team dynamics, and business context—not a sanitized textbook prompt.
Form Your Own Answer
Pause and think through your approach before seeing ours. This active recall is what builds interview muscle memory.
Compare Bad / Good / Best
See exactly why a “Senior” answer falls short of the “Principal” bar. Each criterion is broken down with the interviewer's rubric.
Internalize the Gap
Reflection prompts and a mock interviewer dialogue help you absorb the patterns that distinguish principal-level thinking.
Free Sample Scenarios
Experience the full interview simulation format. These are real scenarios at the Principal bar—not watered-down teasers.
Distributed Rate Limiter
Design a rate limiting system for 5M RPS with sub-5ms latency overhead.
Start scenarioMicroservices vs Monolith
Navigate the build vs. migrate decision with real constraints and team dynamics.
Start scenarioAPI Performance Crisis
Debug latency spikes in production with real metrics and time pressure.
Start scenarioInvest in your next role.
Less than one hour of interview prep coaching—delivered every day for a month.
Monthly
Full access, cancel anytime
- ✓ Daily Interview Scenarios
- ✓ Full Archive Access
- ✓ Bad/Good/Best Analysis
- ✓ Cancel Anytime
Annual
$15/mo · Save 2 months
- ✓ Everything in Monthly
- ✓ 2 Months Free
- ✓ Priority Feature Access
- ✓ Interview Prep Commitment
7-day money-back guarantee. No questions asked.
Common Questions
Is this for New Grads or Junior Engineers?
No. This product explicitly assumes 8+ years of experience. We do not explain basic concepts. We focus on the nuanced tradeoffs expected at Staff/Principal levels in Big Tech.
Does this include coding puzzles?
No. We focus exclusively on System Design, Architecture, Tradeoffs, Operational Reality, and GenAI/AI Engineering.
How does the daily format work?
Every day at 6 AM UTC, you receive a new scenario by email. Read the context, form your own answer, then reveal our Bad / Good / Best analysis to calibrate your thinking. Each scenario takes about 30 minutes.
What happens after I subscribe?
You'll receive a welcome email and your first scenario immediately. From then on, a new scenario lands in your inbox every morning. You also get full access to the archive of all past scenarios.
Can I binge the archive instead of doing one per day?
Yes. Paid subscribers have full archive access. That said, the daily cadence is intentional—spaced repetition builds deeper pattern recognition than cramming.
How is this different from system design books?
Books teach you how systems work. We show you how to answer about them at the Principal level. Every scenario includes a side-by-side comparison of what a weak, competent, and exceptional answer looks like—so you can calibrate where you stand.