❯ arena · learn by playing

Arena.

A daily challenge, weekly leagues and quick games, all built from the course. Every answer you get right here is something you'll get right in an interview.

read the guide →

level–

daily streak–best 0d

this week–local pts · guest

leagueL1Intern3,589 questions in the bank

Arena games

60–90 second rounds. Best scores stay in this browser.

arena · 90s+40 xp
Latency LadderOrder the numbers every engineer should know, L1 cache to a cross-continent round trip.
taught inW00 · Part 1 · Fundamentals W00 · Part 4 · Networking
play →
arena · 75s+40 xp
Pick the StoreA use case drops in. Send it to the datastore that fits before the clock runs out.
taught inW00 · Part 2 · Building blocks W01 · Preview · Storage trade-offs
play →
arena · 75s+40 xp
Fix the OutageSymptom on the left, pattern on the right. Name the fix that stops the bleeding.
taught inW02 · Day 1 · Timeout hell W02 · Day 2 · Idempotency
play →

Playground

The Engineering Playground, mapped to the lessons.

playground+60 xp
Cache or MissBeat LRU at eviction.
taught inW04 · Day 1 · Caching patterns W04 · Day 5 · Multi-tier caching
play →
playground+60 xp
Hash RingAdd a node, move the fewest keys.
taught inW01 · Day 1 · Partitioning W01 · Day 4 · Hot keys and skew
play →
playground+60 xp
Trip the BreakerYou can't see the service while it's open.
taught inW02 · Day 3 · Circuit breakers
play →
playground+60 xp
Back of the EnvelopeEstimate WhatsApp-scale in seconds.
taught inW00 · Part 3 · Estimation W10 · Day 4 · Capacity planning
play →
playground+60 xp
Race ConditionDouble-book a seat, then fix it.
taught inW05 · Day 1 · Consistency models W02 · Day 2 · Idempotency
play →
playground+60 xp
Incident CommanderThe pager just went off.
taught inW10 · Day 5 · Incident management W10 · Day 3 · Deployment strategies
play →

Arena.

5 questions.
20 seconds each.

Arena games

Playground

Arena.

5 questions.
20 seconds each.

Arena games

Playground

Arena.

5 questions.20 seconds each.

Arena games

Playground

Arena.

5 questions.20 seconds each.

Arena games

Playground

5 questions.
20 seconds each.

5 questions.
20 seconds each.