Lab
Systems you can break in your browser. Each drawing is its lab as its page opens, from the same run.
Backfill a week of reports
A nightly job counts the bakery's orders, one run per day. Fail a load, rerun a day, backfill the week, and check every total against the source.
Loads that overwrite their day: the week’s report counts 2,012 orders, as the source does, instead of 2,108.
Stampede a cache
Hundreds of readers ask for the bakery's menu when its cache entry expires. Coalesce, serve stale, refresh early or jitter, and watch the database.
When the menu expires at 3.0 s, coalescing has the database fetch it once instead of 23 times.
Crash the workers behind a queue
A broker hands the bakery's orders to three workers. Crash one mid-order, and choose when they acknowledge, to see work lost, done twice, or done once.
With an idempotency key, worker 2’s crash prints order 18 once: 25 orders done in 4 s, none lost or printed twice.
Break a Raft cluster
Five servers keep one log with Raft. Crash them, split the network and lose messages in your browser, and watch every safety property hold.
All five safety properties held over 249 events.
Plan a bakery’s deliveries
A bakery, its vans and the day’s orders. VROOM plans the routes in your browser, on OpenStreetMap roads, and the map shows the driving it saves.
A busy Saturday: 3 h 12 min of driving instead of 5 h 34 min.