STEM
“The team has already tried adding X to the system prompt, but the failure keeps recurring.”
DECODER →
ANSWER PATTERN
Centralize the fix in infrastructure — don't add another prompt instruction.
Infrastructure vs prompt
plinthprep.com · CCA-F prep
Pass the Claude Architect exam.
1207+ practice questions, a full 60-question mock at the official domain weighting, a weak-spot drill that learns from your answers, and 493+ Leitner flashcards. Built for the Claude Certified Architect — Foundations (CCA-F) exam by people who passed it.
No card required. Try 20 questions free; sign in to track progress; upgrade for the full pool.
plinthprep.com/dashboard
Ready0
Projected · 858/1000Clears the 720 pass. Resume drill →
412
Answered
76%
Lifetime
8d
Streak
124
Mastered
Web · mobile coming soon
1,207
Practice questions
493
Flash cards
19
Compendium sections
720
Pass threshold
HOW IT WORKS
A loop that gets sharper every session.
The same loop that a great human tutor would run: assess, target weakness, simulate the real thing — repeat.
01
Take a diagnostic quiz
Random or domain-targeted, your length. Plinth tracks every answer so it knows what you struggle with.
02
Drill your weak spots
Plinth surfaces the themes you miss most and builds drills around them — not a generic practice set.
03
Sit a full mock exam
60 questions, 120 minutes, real domain weighting, 720/1000 to pass. See exactly where you stand.
On your phone — coming soon
Drill weak spots between meetings.
The same quiz pool, the same mock exam, the same weak-spot drill — on iOS and Android. Progress syncs across devices the moment you answer. Apps launch later this year; web access is included with your purchase today.
- One-tap drillOpen the app, tap Drill, run five questions while the kettle boils.
- Flashcards anywhereLeitner spaced repetition follows you device-to-device.
- Native iOS + AndroidReal apps, not a web wrapper. Offline once cached.
Coming soon — apps launch later this year.
SyncReal-time
STEM DECODER · UNIQUE TO PLINTH
Read once. Know the answer type.
Decode the test, not just the content. The CCA-F exam reuses predictable stem-phrase → answer-pattern mappings. Plinth's 17-section Stem Decoder library is the lookup table that turns every question into a 5-second pattern match — instead of a three-pass re-read.
- 17 sections covering the most repeated stem signals
- Each pattern: stem keyword → answer pattern → why
- Cross-linked to drill packs so you can practice on demand
STEM
“Production runs work, but the eval suite reports inconsistent JSON keys.”
DECODER →
ANSWER PATTERN
Structure the tool response shape, not the few-shot examples.
Reliability hierarchy
STEM
“Where should this guardrail logic live — in the model, the orchestrator, or the tool?”
DECODER →
ANSWER PATTERN
Layer placement — choose the layer that owns the invariant.
Layer placement
FEATURES
Built like a serious study tool, not a quiz app.
Plinth's design choices come from how high performers actually study: spaced repetition, deliberate practice on weak spots, and a single readiness number you can trust.
Weak-spot intelligence
Every answer feeds a theme-level model of what you don't yet know. Drills are auto-built around your weakest themes — not the test's median.
Two-mode mock exam, 13 scenarios
Same 60-question count, same 120-minute window, same domain weighting as the real exam. Standard mode pulls from the 6 official scenarios; Comprehensive mode draws from all 13 (6 official + 7 extended). Auto-graded with a /1000 scaled score.
Hints on every question
1,200+ Stem Decoder hints — 100% pool coverage — with 2-stage progressive disclosure (L1 pointer first, L2 pattern reveal on click). Keyed to a 17-section reference doc grounded in Anthropic's Engineering blog, Claude Code docs, MCP docs, and the public CCA-F exam guide.
Leitner-style flashcards
493+ cards across 5 spaced-repetition boxes. Hard/Good/Easy ratings advance cards at different paces. Reverse-mode supported.
Dashboard + hint analytics
Real-time readiness, per-domain mastery, lifetime accuracy trend, pace-to-exam projection — plus a 'Where you used hints' widget that shows reliance by scenario × level (Numbers ↔ Chart toggle). Every chart is computed from your actual data, not demo numbers.
Bilingual — EN · 한국어
Every question, every hint, every UI string is available in both English and Korean. Per-page locale toggle lets you peek at the other language without changing your app preference. Real Korean translations (no phonetic transliteration).
Lifetime updates, grandfathered in
Pool grew from 700 → 1,200+ this cycle. Every new question, every Stem Decoder amendment, every feature we ship — you get it all for the original $20, forever. No subscription, no upgrade fee.
Mobile sync
Native iOS and Android apps with cross-device sync. Sessions, hints used, dashboard, history — all follow you between web and mobile via your account.
PRICING
One price. Everything unlocked. Forever.
No subscriptions, no upsells, no per-feature paywalls. Pay once, study until you pass — then keep your account for the next exam cycle.
PLINTH PRO · ONE-TIME
$20one-time
Web
- Full 1207+ question pool, growing every cycle
- Unlimited mock exams at official 60Q / 120-min weighting
- All 493+ Leitner flashcards with reverse-mode
- Weak-spot drills that adapt to your answers
- Lifetime dashboard, history, and per-domain mastery
- Compendium, Stem Decoder, Modules library
- Mobile sync (app coming to App Store / Play Store)
Mobile app price will be $25 via App Store / Google Play when it launches.
FAQ
Common questions.
What people ask before they sign up.
Is there a free trial?+
Yes — 20 questions and 20 flashcards anonymously, no signup required. After that, an account is Plinth Pro ($20 lifetime). There's no free signed-in tier.
How many questions are there?+
Several hundred original practice questions across all five exam domains, plus weak-spot drill seeds and admin-curated imports. Exact counts are derived from the data so they're always current.
Are the questions official?+
No — these are practice questions written by people who passed the CCA-F exam, designed to drill the same concepts. The mock exam mirrors the official 27/18/20/20/15 domain weighting and 720/1000 pass threshold.
Does my progress sync across devices?+
Yes, once you have an account. Quiz sessions, flashcard progress, and lesson read-state all sync to your account. Anonymous use stays on this device.
Refund policy?+
All sales are final. Use the free preview to evaluate before you buy. Once you purchase, you get lifetime access — including every new question, every new feature, and every Stem Decoder update we ship from here on out. No subscription, no upgrade fee, no expiration.
START IN 60 SECONDS
Walk into the exam already knowing you'll pass.
20 free questions. No card. Sign in to track progress and unlock everything.