How a Belgian Food App Fixed Rider 'Teleporting' Bug Using Event-Stream Architecture

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Developers at MealApp, a restaurant marketplace based in Antwerp, encountered a critical real-time tracking failure in production where delivery riders appeared to 'teleport' on customers' screens. The root cause was treating rider location as a single mutable value rather than an ordered sequence of events, which caused out-of-order network packets and race conditions across multiple servers to corrupt location state. The team resolved the issue by switching to an append-only Redis stream model that uses client-side timestamps for ordering and discards late-arriving updates on both server and client. The fix also introduced server-side status guards to prevent order status from regressing, ensuring UI consistency. As an unplanned benefit, the event log generated rich analytics data on prep times, rider wait times, and delivery bottlenecks at no additional engineering cost.

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