I'm currently running two RDS Postgres databases on the t3 instance family and planning to upgrade them to the t4g instance type. Since these databases are crucial for 24/7 operations and are already set up in Multi-AZ mode, I'm concerned about any potential downtime during this transition. Is there a method to migrate to the new instance type while avoiding downtime altogether?
4 Answers
One way to minimize downtime is to add a read replica using the new instance type. If your application connects via a cluster endpoint, you can promote the read replica to replace the old writer. This process typically takes about 10-15 seconds.
Using an RDS proxy with your Multi-AZ database can also help reduce the switching time during updates, making transitions smoother.
The blue/green deployment strategy is often recommended for this type of migration. It allows you to validate any downtime in a development environment before you make the switch in production. It's a good way to ensure that there are minimal disruptions to your services.
Just a heads up, even with the blue/green method, there might be a few-second delay when DNS gets updated. While it's usually under a minute, make sure that the potential downtime fits within your tolerance level.
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