Pay for live AI evaluation, not for practice.
Most of Fault Tolerant is free: the canvas, the problem library, learning tracks, and puzzles. Credits are only spent when the AI interviewer responds to you live or grades your design.
Free
Start building your design reflex.
3 timed interviews to try
- 15 AI credits per month
- 3 timed interviews to try
- 200+ distinct practice problems
- Daily architecture puzzles
- Learning tracks
Pro
For engineers actively interviewing.
≈40 full AI-led interviews/mo · 400 AI credits
- 400 AI credits per month
- ≈40 full AI-led interviews a month
- Everything in Free
- Detailed readiness breakdown
- Priority AI evaluation
Pro Annual
Same Pro credits, billed yearly.
≈40 full AI-led interviews/mo · 400 AI credits
$120/year (2 months free)
- 400 AI credits per month
- ≈40 full AI-led interviews a month
- 2 months free vs monthly
- Everything in Pro
Max
Heavy practice and team-prep mode.
≈120 full AI-led interviews/mo · 1,200 AI credits
- 1,200 AI credits per month
- ≈120 full AI-led interviews a month
- Everything in Pro
- Higher concurrency
Secure checkout by Paddle.
Paddle is our Merchant of Record — it handles payment, taxes, and invoices. Cancel any time from your Billing page.
How credits work
1 credit = 1 live AI turn
Every live interviewer response and every full AI design review consumes one credit.
Practice never costs a credit
Drawing, autosaving, the problem library, learning tracks, and puzzles are unlimited on every plan.
Credits reset monthly
Your allowance refreshes every billing month. Unused credits do not roll over.