Node.js streams: flow control, piping, and object mode
Readable, Writable, and Transform streams, .pipe() versus stream.pipeline(), what backpressure protects, and how object mode changes the rules. Each answer comes with code we...
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Offline web apps: caching, queued writes, and conflict resolution
A local-first app works without a network and treats the connection as a bonus. This quiz covers service-worker caching strategies (cache-first, network-first,...
PostgreSQL performance: read the query plan
Thirty questions about diagnosing PostgreSQL performance from real EXPLAIN ANALYZE output. Covers index design, sequential scans, cardinality estimates, composite-index order,...
Predict the physics: what happens when you let go?
A chain leaps out of a jar before it falls. A water drop lasts longer on a hotter pan. A handle spun in orbit flips over and back on its own. A ball on the longer, curvier...
Probability paradoxes: Monty Hall, the birthday problem, and more
Monty Hall, the birthday paradox, the gambler's fallacy, and other puzzles where the math disagrees with your gut. Each question offers a tempting wrong answer, and each...
Programmer habits under the microscope: Fridays, night owls, swearing and music
Don't deploy on a Friday. Real programmers work at night. Swearing in comments means messy code. Music ruins concentration. Researchers have tested all four with commit...
Project management failure modes
A scenario-based quiz about why projects slip, grow, stall, or become confusing. Each Question names a recognizable project smell and uses the Explanation to teach the...
React: when does this re-render?
Thirty-two code-driven questions about render snapshots, Effect synchronization, identity, memoization, refs, React 19 Server and Client Components, use(), and Suspense. Assume...
Read the Git graph: commits, parents & what rewriting really does
Git is a graph, not a timeline. Almost every confusing thing it does makes sense the moment you can see the parent pointers. This quiz gives you the graph before a command and...
Read the sky: clouds as a six-hour forecast
Every cloud shows you something the air is doing. Work out what an anvil, a lens over a ridge, a ring around the sun, or a row of hanging pouches tells you about the next few...
Reading a broken metal part: fatigue, fracture, corrosion, creep
Metal parts break in a few recognisable ways, and each one leaves clues on the broken face. Read real failure photos and learn to tell fatigue, brittle cleavage, ductile...
Reading old paintings: symbols, perspective and anachronism
Paintings made before 1900 were meant to be read. A sleeping dog means fidelity, a lamp that has just gone out means time is up, and a vanishing point tells you where the...