Ably has introduced idempotency across all its client library SDKs, ensuring that realtime messages will only be published once even if there are client or connectivity failures causing reattempts. This feature is implemented by associating a unique identifier with each message and preventing duplication upon further attempts to publish with the same ID. Idempotency helps in maintaining data integrity and reducing inconveniences caused by accidental duplication of messages, especially for critical realtime operations like payment systems or in-play bets. To implement idempotency, developers can provide a unique message ID when publishing or enable idempotent publishing for automatic retries by the SDK.