Level 2 of 5

Ascent

The simple answers stop here. Systems that span multiple services, fail in non-obvious ways, and demand you think about reliability — not just correctness.

ASCENT

Notification System

Design a notification system — push, SMS, and email delivery at 5M sends/sec. Multi-channel fan-out, retry/DLQ, scheduled delivery, fault isolation per provider.

Kafka Fan-out Per-Channel Workers Retry / DLQ Bloom Filter Scheduling Circuit Breaker

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ASCENT

Pastebin

Design pastebin.com — paste text, get a short link, retrieve by anyone. 10M DAU, expiring pastes, large blobs.

Content-Addressable Storage Ref Counting Async S3 Upload Expiry Jobs State Machine

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