All information stored is discarded when the process ends. This can result in more-than-once message delivery.
The non-durable gateway deduplication persistence uses a least-recently-used (LRU) cache. By default this cache can contain up to 10,000 items. The maximum size can be changed using the following API:
var gatewayStorageConfiguration = new InMemoryDeduplicationConfiguration
{
CacheSize = 50000
};
endpointConfiguration.Gateway(gatewayStorageConfiguration);