75 curated questions graded from Foundations (Easy) to Practical Patterns (Medium) and Internals & Architecture (Hard).
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Foundations & Core Concepts
PRIMARY KEY creates a unique B-tree index + NOT NULL implicitly.SERIAL legacy pseudo-type creating sequence default; GENERATED ALWAYS AS IDENTITY SQL-standard preferred (protects against manual id inserts).WHERE col <> 'x' excludes NULLs!) - explicit IS NULL/IS NOT NULL required.COALESCE(a,b,c) first non-null; NULLIF(a,b) returns null when equal (divide-by-zero guard pattern).Get instant access to all 25 questions, in-depth model answers, code sandboxes, and all 27+ technologies for a single one-time payment.
Core concepts, definitions, basic syntax, and first principles expected in round 1 screening.
Real-world mechanisms, state management, edge cases, performance trade-offs, and practical coding.
Deep runtime internals, memory models, distributed design, concurrency failure modes, and architectural decisions.