Fundamentals Round
Quick questions on SQL, security, concurrency, and how systems fail. Some companies run it as its own screen; most fold it into the coding and design rounds.
Start a Session
Set a level to tune the cards. Cards you rated Shaky come up more often.
How It's Graded at Each Level
- Junior
Correct joins and aggregates, the common web security risks, and what a race condition is.
- Mid
Window functions, auth and session handling, and the usual concurrency fixes.
- Senior
Isolation levels, distributed failure modes, and the tradeoff behind each answer.
- Staff
The same depth, tied to decisions you made and what you'd change at larger scale.
- Principal
Seldom a separate round. Expect these topics inside design and leadership conversations.
Drill Types
- SQLJoins, window functions, and NULL traps in Postgres.About 2 min a drill
- SecurityOWASP, auth, JWT, and CSRF.About 1 min a card
- Systems and ConcurrencyConcurrency, distributed systems, databases, and networking.About 1 min a card
- TechniquesMatch a production problem to its idiom: backoff, idempotency, or leases.About 1 min a card
- TradeoffsPick a side of a classic tradeoff and defend it.About 2 min a card
- ConceptsRecall a concept from memory, then reveal and check.About 1 min a card
- FlashcardsPattern definitions and when to reach for each one.30 sec a card
Read These First
All Library Pages- ConceptACIDConcept
- ConceptIsolation LevelsConcept
- GuideSQL ReferenceGuide
- GuideSecurity ReferenceGuide
- TechniqueCircuit BreakerTechnique
- TechniqueToken BucketTechnique
Common Mistakes
Memorized definitions only
Each answer needs one example of when it matters.
Skipping the tradeoff
Say what the choice costs, then say when you'd pick the other one.
Guessing on security
Name the attack, then the specific defense.
Matching Mock
Mixed Timed Drill
A timed set of cards from several rounds, with a report at the end.