Scale Lab — Interview problem: realtime chat Advanced

Chat differs from the earlier problems because clients hold connections open for a long time. Gateways are sized by the number of open connections, not by requests per second, and every message sent must still reach a recipient connected to a different gateway.

• Results include three extra criteria: how long a message takes to arrive, how many messages never arrive, and what percentage of clients the system still has room for.
• Click the Gateway to enable reconnect with jitter.

Why reconnecting clients need backoff and jitter: Retry, backoff and jitter. Capacity and pricing assumptions are the same as in Scale Lab.