Technology is described for a durable and provably complete archival of streaming data for a potentially indefinite retention period. According to the present technology, streaming data may be prepared for storage to meet completeness and consistency requirements that may result in once-and-only-once delivery and serialization of the streaming data. In one example, a storage preparation service may archive a data stream in real-time to a first data store that provides eventual write consistency and use another data store to provide a consistent view of the data. The storage preparation service may capture metadata that satisfies the completeness requirements and may provide conflict resolution to ensure write consistency.