A celebrity posts and 50M followers need a notification. The hard parts are not sending one message, they are fan-out strategy, deduplication, channel routing, and not flooding users. Here is the architecture that handles both the long tail and the viral spike.
Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.
A celebrity posts and 50M followers need a notification. The hard parts are not sending one message, they are fan-out strategy, deduplication, channel routing, and not flooding users. Here is the architecture that handles both the long tail and the viral spike.
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