Realtime Checks and Presence Accuracy for Auction Notification Streams
Short answer: use a realtime API surface that matches authorization checks, but make the data contract own expiry, reconnect, duplicate delivery, and recovery for auction bidder notifications. Endpoint selection comes second. The deciding constraint is presence accuracy: the server must be able to distinguish a bidder who may receive a lot update from a socket that merely happens to remain…
The article discusses the importance of separating realtime authorization checks from auction bidder notifications in a server-side architecture. It emphasizes the need for a clear distinction between four key components: connection status, subscription authorization, auction-specific visibility, and event handling. To achieve this, the server should maintain records containing the principal ID, auction ID, allowed lots, expiration time, and a subscription epoch.
Each business event should have its own stable event ID and auction cursor, allowing for proper recovery and avoiding duplicate processing. The article highlights the significance of fail-closed expiry, monotonic replacement, idempotent application, and bounded recovery as invariants for a robust system. It also mentions the need to test various failure scenarios, such as token expiration while the connection remains open or cursor out-of-order arrival.
The choice of transport (e.g., Ably, Pusher Channels, PubNub, or self-managed WebSocket service) should be based on how well it can support the defined invariants and operational constraints.
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