System design / 4 simulations
Queues, Kafka and Streaming
Queues, logs and pushing updates to users.
Open the lab → Change the load, break a part, watch what happens. Free, no sign-up.
All topics: async and streaming
- A message queue between servicesBeginner · 6 min
Backlog, consumer capacity, retries and dead letters. See why queues absorb bursts but not overload.
- Kafka: a log, not a queueIntermediate · 9 min
Partitions, keys, consumer groups, lag, rebalancing and replay, in seven guided steps.
- Polling, long polling, SSE or WebSocketsIntermediate · 6 min
Four ways to push updates to a browser, on the same events: delay, requests and connections compared.
- Real-time analytics: windows and watermarksAdvanced · 6 min
Count clicks in 10-second windows as they stream in. The watermark trades complete counts against how fast results appear.