Senior Track
Practice
Theory teaches the shape. Practice makes it stick. Each card here is a short problem you commit to an answer on before any explanation appears — that commitment is what builds the senior reflex.
How to use Practice. Pick a category, look at the code or scenario, form an answer in your head, then reveal. The most valuable part is usually the breakdown of why the wrong picks were wrong. Coming back to the same cards weeks later is when the patterns stop feeling new.
Spot the Tax
20 cardsCode that works today and costs something specific in six months. Look at the snippet, predict the cost, reveal the principle. Reveal-only format.
Reading the Source
5 cardsMultiple-choice drills on how Rails actually works behind the magic. Discrete answers, wrong picks explain themselves.
Scaling
8 cardsOne scaling-bug shape per card. Index design, N+1, caching, pagination, contention, concurrency, jobs, bulk operations.
SOLID
10 cardsDesign-judgment cards, two per principle. The "answer" is a shape, not a discrete pick.
Payments
6 cardsThe shapes that show up in real payment integrations: idempotency, webhook verification, async confirmation, refund modeling, event ordering, ledger picks.
Interview Prep
6 cardsCommon senior Rails interview questions with answer rubrics. Each card explains what the right answer signals to the interviewer (and what the wrong ones do too).