Scale Lab — Interview problem: a notification system Intermediate
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Sending messages sounds simple until the provider goes down. Three rounds, each adding one requirement: fast, then no losses, then no duplicates.
- Click the Worker to enable retries and duplicate-send protection.
- Results include two extra criteria: the number of lost messages and the number of duplicate sends.
Why a queue gives at-least-once delivery and the consumer must be idempotent: Idempotent consumer. Capacity and pricing assumptions are the same as in Scale Lab.