In modern flight booking systems, streaming fare updates and reservations through distributed microservices is common. These pipelines must be retry-resilient, ensuring that transient failures or replays don’t cause duplicate bookings or stale pricing. A core strategy is idempotency: each event (e.g., a fare-update or booking command) carries a unique identifier so processing it more than once has no adverse effect.
In practice, this means assigning a unique event ID or idempotency key to each fare request. For example, an airline booking API might attach a unique request token so that if a user’s retry comes through, the service recognizes and ignores it. This prevents duplicate bookings if, say, a payment call times out and is retried. Similarly, pricing events should include a unique price-update ID. Downstream consumers (cache updaters, booking services, analytics) record these IDs (in a database or distributed cache) and skip any event with an already-seen ID.