p99 184ms
System design studioSee where your architecture breaks.
Design on a live canvas, inject traffic and failures, and watch latency accumulate across every path.
Explore the labBuilt for senior engineering careers
Don't just prepare. Practise the real work.
Master system design, incident response, and staff-level judgment in a workspace that reacts to every decision you make.
★★★★★
Built with senior engineers, not test-prep tricks.
Consequence-based feedback
Clients12k req/s
API cluster+18ms · 43%
Event queue+6ms · 21%
Redis cache+46ms · 87%
Postgres+114ms · 74%
Failure injectedCache cold start
End-to-end p99184ms42ms over budget
Your strongest signal: operability
One workspace for the skills that decide senior careers
Private by default No single right answer Verified human mentors Real engineering scenarios
Practice that transfers to the job
Build the judgment that senior roles actually reward.
Every exercise gives you a realistic system, real constraints, and feedback on the consequences of your decisions.
Root cause found
Incident simulatorDebug like you are on call.
Investigate realistic logs, metrics, traces, and failure cascades under a ticking incident clock.
Explore the labStaff signal +18%
Career scenariosPractise the decisions nobody teaches.
Build influence, scope ambiguous work, write promotion evidence, and communicate through conflict.
Explore the labYour career signal, made visible
Turn practice into proof.
CareerPetal tracks how you reason, communicate, and improve—then turns that progress into evidence you control.
- See growth by skill, not vanity streaks
- Keep every design and review private by default
- Share selected work with mentors and recruiters
Readiness signalSenior backend
Top 18%82+12 this month
40+real-world drills
5senior skill tracks
< 1sfeedback preview
0puzzle grinding
Designed with practising engineers
Serious practice. Zero theatre.
“The first practice tool that responds to the trade-offs I made—not whether I copied one diagram.
“It feels like doing the work, not studying content about doing the work.
“The incident lab exposed how quickly I jump to fixes before forming a hypothesis.
Simple, transparent pricing
Start free. Upgrade when the work gets serious.
Explorer
Build a real practice habit.
$0
- Weekly engineering teardown
- Peer mock matching
- Starter scenario library
- Public skill profile
Most popular
Pro
Prepare for your next level.
$15/ month
Billed annually- Full system design studio
- 20 AI critiques each month
- Incident and staff-track labs
- Private progress analytics
- Everything in Explorer
Mentored
Add expert human feedback.
$79/ month
Billed annually- One verified mentor session
- Personal growth roadmap
- Async design review
- Everything in Pro
Private beta opening soon
Engineer your next level.
Join the build list for early scenarios, product previews, and founding-member pricing.