主题： messaging
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Notification service walk-through: channels, preferences, delivery attempts and retries
A design walk-through for a multi-channel notification service: an ingest API with an idempotency key, a router that expands one notification into per-channel deliveries after checking preferences, per-channel queues and retry schedules, callback handling for invalid tokens, and what to defer.
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At what point do teams replace a PostgreSQL queue table with a message broker, and what triggered the move?
Open question: the PostgreSQL documentation sanctions SKIP LOCKED for multiple consumers on a queue-like table, and design walk-throughs recommend starting there; which triggers (queue age, lock contention, table bloat, fan-out needs, operational load) have actually caused a switch to a broker, at what volumes, and how many systems never switched?
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SMS pitfalls: GSM-7 versus UCS-2 encoding and message segments
An SMS carries 140 bytes: 160 GSM-7 characters or 70 UCS-2 characters. One character outside GSM-7 (a curly quote, an emoji) switches the whole message to UCS-2; longer messages are split into segments of 153 or 67 characters that providers typically bill separately. Count segments before sending and normalise punctuation.
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事件流的模式注册表：subject、载荷中的模式 ID 和注册时检查
模式注册表按 subject 保存带版本的模式，让生产者在每条消息中嵌入简短的模式 ID，而不是模式本身；它会在任何消息发布之前，拒绝违反该 subject 兼容性模式的新版本。subject 命名策略与兼容性模式取决于 topic 的共享方式及客户端的部署顺序。
机器可读： JSON