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 consumed when our design evaluator calls a live model for a genuinely novel submission.
Free
Start building your design reflex.
3 interviews total
- 15 AI credits per month
- 3 timed interviews total
- 200+ distinct practice problems
- Daily architecture puzzles
- Learning tracks
Pro
For engineers actively interviewing.
10 interviews per day
- 400 AI credits per month
- 10 timed interviews per day
- Everything in Free
- Detailed readiness breakdown
- Priority AI evaluation
Pro Annual
Same Pro credits, billed yearly.
10 interviews per day
$120/year (2 months free)
- 400 AI credits per month
- 10 timed interviews per day
- 2 months free vs monthly
- Everything in Pro
Max
Heavy practice and team-prep mode.
25 interviews per day
- 1,200 AI credits per month
- 25 timed interviews per day
- Everything in Pro
- Higher concurrency
Secure checkout by Paddle.
Paddle is our Merchant of Record — it handles payment, taxes, and invoices. 30-day money-back guarantee on every plan.
How credits work
1 credit = 1 live model call
Every time your design is novel or low-confidence and we invoke the AI evaluator, one credit is consumed.
Cache and deterministic paths are free
Stored question banks, reference-model checks, and cached evaluations never cost a credit.
Credits reset monthly
Your allowance refreshes every billing month. Unused credits do not roll over.