On September 10th, Amazon announced the general availability of Quantum Ledger Database (QLDB), a ledger database based on blockchain technology. As such, QLDB provides a fully managed ledger which can contain multiple tables, implementing an immutable transaction journal, which is cryptographically verifiable, and owned by a centralized trusted authority.
First announced during AWS re:Invent 2018 together with Amazon Managed Blockchain, Amazon Quantum Ledger Database allows creating a database which only accepts insert and select statements, without the option of updating or deleting data. Moreover, QLDB uses the SQL-like query language PartiQL, providing a familiar experience for working with the information, while taking advantage of the capabilities which a ledger database brings. The service supports both structured and unstructured documents, including nested data. Furthermore, to ensure no one has tampered with the stored data, Amazon provides an API used to verify these by providing a digest of the entries, and the details of a document.
Source: https://aws.amazon.com/blogs/aws/now-available-amazon-quantum-ledger-database-qldb/
Many distributed blockchain solutions, such as Bitcoin, Ethereum, and Azure Blockchain Service, differ from QLDB in a range of aspects. For example, they focus on providing a means for multiple parties to share data, execute contracts, and distribute trust by needing consensus from a wide variety of members of the blockchain. Alternatively, Amazon QLDB instead focuses on providing an immutable record store, keeping track of all changes to the data, while using a centralized authority and provided in a familiar manner using tables, indexes and SQL-like queries. As blockchain technology backs the revisions on the journal, they are cryptographically chained, without the possibility to change or delete them. Consequently, it removes the need to build an auditing trail into traditional relational databases, which helps in improving trust in a simplified manner as explained by David Teich, principal analyst.
The trust in the blockchain model is important, even when a blockchain isn't needed. To have the same kind of trust in a relational database, a lot of extra tables and code in applications to provide the audit trails that are native to blockchain. That extra work impacts both performance and the ability to update and modify the system.
Using a serverless model, pricing of Amazon Quantum Ledger Database is on the used resources, calculated by the number of read and write operations, storage used, and data transfer, without the need for any upfront commitment. Subsequently, it provides interoperability with Amazon Managed Blockchain, where the latter can copy its blockchain's transaction activity into QLDB. Once moved out of the original service and into tables, this then provides the opportunity to analyze the data, without the chance of causing any interference on the original network. Currently, QLDB is available in the regions US East (Ohio), US East (N. Virginia), US West (Oregon), Asia Pacific (Tokyo) and EU (Ireland), with additional locations coming soon.