Notification Service with Idempotency — PayPal

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Notification Service with Idempotency[ OK ] 220 — full content available
[ INFO ] category: System Design  difficulty: hard  freq: high  first seen: 2026-01-13
[HARD][SYSTEM DESIGN][HIGH]data_engineeringDistributed SystemswebSystem DesignBackendmobilebackendinfrastructure
$ cat problem.md
Design a notification service with a specific focus on implementing idempotency to prevent duplicate message delivery.
Key Requirements:
Prevent duplicate notifications
Handle high-volume burst traffic
Scalable architecture
Exactly-once delivery guarantee
Discussion Points:
Event-driven vs synchronous approaches
Stateful stream processing (Kafka/Flink)
Redis for write-through caching
Idempotent ID management
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