Q: What is Amazon Quantum Ledger Database?

Amazon Quantum Ledger Database (QLDB) is a purpose-built ledger database that provides a complete and cryptographically verifiable history of all changes made to your application data.

Q: How is a ledger database different from other databases?

Traditional databases allow you to overwrite or delete data, so developers use techniques such as audit tables and audit trails to help track data lineage. While these approaches can work, they require custom development, can be difficult to scale, and put the onus on the application developer to ensure all the right data is being recorded. Data in Amazon QLDB is written to an append-only journal, providing the developer with full data lineage. Moreover, data in Amazon QLDB's journal is immutable and verifiable, meaning you can trust the data in your ledger.

Q: What data should I store in a ledger database?

Amazon QLDB's features make it a natural fit for system-of-record applications – those for which data integrity, completeness, and verifiability are critical. For example, in the supply chain and logistics space, an application built on Amazon QLDB would have the entire history of changes, such as movement between carriers and across borders, available for query and analysis. In finance, system-of-record applications track critical data, such as credit and debit transactions. Instead of building complex record keeping functionality within their application, banks can use QLDB to easily store a permanent and complete record of all financial transactions.

Q: Is Amazon Quantum Ledger Database a distributed ledger or blockchain service?

Amazon QLDB is not a blockchain or distributed ledger technology. Blockchain and distributed ledger technologies focus on solving the problem of decentralized applications involving multiple parties where there can be no single entity that owns the application, and the parties do not necessarily trust each other fully. On the other hand, QLDB is a ledger database purpose-built for customers who need to maintain a complete and verifiable history of data changes in an application that they own. Amazon QLDB offers history, immutability and verifiability combined with the familiarity, scalability and ease of use of a fully managed AWS database. If your application requires decentralization and involves multiple, untrusted parties, a blockchain solution may be appropriate. If your application requires a complete and verifiable history of all application data changes, but does not involve multiple, untrusted parties, Amazon QLDB is a great fit. If you have a use case for distributed ledgers or blockchain, please see Amazon Managed Blockchain.

Q: What kind of functionality does Amazon QLDB support?

In addition to providing a complete and verifiable history of application data changes, Amazon QLDB supports transactions with ACID semantics, a flexible document data model, and a familiar SQL-like API. QLDB is also fully managed and automatically scales to meet the needs of your application with no provisioning required.