02
Level 2 of 5
Ascent
Async pipelines, multi-channel delivery, Kafka fan-out, blob storage, expiry at scale.
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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