Primary-secondary or master-slave database relationships are common, but have some challenges when failures occur in high-transaction, heavy traffic environments. Databases are taking lots of requests and transactions are being written and read continuously. Backup processes can be taxing and time-consuming. Restoration and synchronization can take significant time. Heavy demand environments can benefit from an active-active database configuration with bi-direction replication to keep data synchronized on both database servers. This type of design does add more complexity but also adds greater levels of redundancy and resiliency within a single site, or across multiple sites, depending on configuration.