Abstract: Methods, systems, and techniques for event notification. An event, such as a payment event that represents a payment transaction having been initiated, completed, or that the transaction is in progress, results in an event engine sending an upstream message to one or more servers. The one or more servers receive the upstream message, which is in a first format. The one or more servers convert the upstream message into a downstream message that is in a second format, such as an ISO 20022 format, and the downstream message is subsequently consumed by an event consumer. The event consumer may consume the downstream message in real-time relative to when the event occurs. Undelivered upstream or downstream messages may be stored in a dead letter channel repository for attempted redelivery.