# How Databases Keep Read-Only Copies Up-to-Date > Amazon's 2016 patent describes a system for efficiently updating read-only copies of a distributed database by sending specific change notifications, ensuring read-only nodes show accurate data. - **Patent:** US 9280591 - **Original title:** Efficient replication of system transactions for read-only nodes of a distributed database - **Owner:** Amazon Technologies Inc - **Granted:** 2016 - **Status:** Active - **Times cited:** 108 - **Field:** software, telecommunications, consumer_electronics, semiconductors ## What it does This patent details how a distributed database system manages updates across multiple nodes. When a change is made to the main database (the read-write node), the system breaks down the update into smaller steps called 'system transactions.' For each transaction, it generates 'change notifications' that list exactly what needs to be altered. Crucially, it marks the very last notification for each transaction. These notifications, including the final one, are then sent to read-only nodes (read replicas). This 'last change' notification tells the read-only nodes precisely when they can present a consistent, updated view of the database to users requesting data, ensuring they don't show outdated information while an update is still being applied. ## What it does NOT cover - Does not cover systems where read-only nodes are updated without specific 'change notifications' indicating the exact modifications. - Does not cover systems that don't identify a specific 'last change' notification to signal the completion of a transaction. - Does not cover scenarios where read-only nodes are updated by sending the entire database state rather than incremental changes. - Does not cover systems where read-only nodes cannot determine a consistent database state for read requests based on the received notifications. - Does not cover updates to read-only nodes that are not part of a larger distributed database system. ## The clever bit The key innovation is identifying and signaling the *last* change notification for each transaction. This allows read-only nodes to precisely know when a transaction is fully applied and the database state is consistent, avoiding the need for complex locking or waiting for all potential changes. ## Real-world examples 1. Amazon Web Services (AWS) database services like RDS and Aurora 2. Distributed database systems with read replicas 3. High-availability database architectures ## Why it matters This patent is foundational for modern cloud database services, enabling services like Amazon RDS and Aurora to provide highly available and consistent data. Efficiently replicating data to read replicas is critical for scaling database read performance and ensuring data integrity in large-scale systems. ## Frequently asked questions ### What does How Databases Keep Read-Only Copies Up-to-Date cover? Amazon's 2016 patent describes a system for efficiently updating read-only copies of a distributed database by sending specific change notifications, ensuring read-only nodes show accurate data. ### Who owns patent US 9280591? Amazon Technologies Inc owns this patent, granted in 2016. ### When does this patent expire? This patent is expected to expire on March 8, 2036, when the invention enters the public domain. ### What is patent US 9280591 cited by? This patent has been cited by 108 later patents that build on its ideas. ### What problem does this patent solve? This patent is foundational for modern cloud database services, enabling services like Amazon RDS and Aurora to provide highly available and consistent data. Efficiently replicating data to read replicas is critical for scaling database read performance and ensuring data integrity in large-scale systems. ### What does this patent NOT cover? Does not cover systems where read-only nodes are updated without specific 'change notifications' indicating the exact modifications. **Full plain-English explainer:** https://patentbrief.org/patent/us/9280591/amazon-emr-elastic-mapreduce **Original patent:** https://patents.google.com/patent/US9280591 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Amazon Delivers Content Faster Using Local Servers](https://patentbrief.org/patent/us/9332078/facebook-memories) — Amazon's 2016 patent describes a system for breaking down digital content into smaller pieces and storing them on servers located near users to speed up downloads and reduce network traffic. - [How to Keep Backup Data in the Correct Order](https://patentbrief.org/patent/us/9811430/aws-codepipeline) — A method for ensuring that backup data arrives at a secondary storage location in the exact same sequence it was created at the primary location to prevent data corruption. - [How Software Automatically Translates Database Queries for Different Storage Systems](https://patentbrief.org/patent/us/9535948/facebook-watch) — A system that intercepts database queries written for traditional relational databases and automatically translates them to work with non-relational databases, allowing developers to switch storage systems without rewriting their application code. - [How Software Services Pass Messages Across Different Network Zones](https://patentbrief.org/patent/us/6073184/method-of-transmitting-a-notification-to-a-receiver-from-plural-notification-services-in-a-distributed-application-network-and-a-network-for-implementing-the-method) — A method for letting different parts of a large software network communicate by linking their notification services together like a relay race. - [How to Keep Data Safe During a Site Failover](https://patentbrief.org/patent/us/9672117/aws-codedeploy) — A method for keeping data backups synchronized and accessible even when a primary data center goes offline and systems must switch to a backup location.