تأثيرات مرة واحدة بالضبط (Exactly-once effects)

في هذا الدرس

distinguish unavailable exactly-once delivery from designable exactly-once effects.

الموضوعات المخطط لها

• Over an unreliable network a sender cannot know whether a message arrived, so it retries; delivery is at-least-once or at-most-once.
• Exactly-once effects: make duplicates harmless with idempotency keys, deduplication tables, and conditional updates.
• Some platform features (for example Kafka transactions) give exactly-once processing inside their own boundary; effects outside, such as charging a card, still need idempotency. Verify the guarantees for your versions.
• Pass an idempotency key to external providers and store the result per key.