Is there any complete way to zdp Aurora MySQL DB?

Question

Hi, 
We have applications(multi Datasource config with master, slave) with AWS Aurora RDS MySQL Clusters with Multi-AZ (1-writer instance, 1-readonly instance)

When we scale up our DB instances, firstly we scale-up our read-only instance.
From here, it is not a problem because writer instance can also perform as read instance.
But when we scale up our writer instance, failover occurs, writer instance is changed to read-only replica and connections with writer instance are remain for writing operations after failover.

How can I avoid downtime with this case?

Riku_Kobayashi · Answer

I think we have to allow for downtime due to failover caused by instance class changes, as it is inevitable.  
Aurora DB failover takes a short time.  
It would be a good idea to stop the service during that time.  
https://aws.amazon.com/rds/aurora/faqs/?nc1=h_ls  
> If you have an Aurora Replica in the same or a different AZ when failing over, Aurora flips the canonical name record (CNAME) for your DB Instance to point at the healthy replica, which is promoted to become the new primary. Start-to-finish, failover typically completes within 30 seconds. For improved resiliency and faster failovers, consider using Amazon RDS Proxy which automatically connects to the failover DB instance while preserving application connections. Proxy makes failovers transparent to your applications and reduces failover times by up to 66%.

From the documentation here, it is difficult to avoid downtime.  
https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Aurora.Modifying.html#Aurora.Modifying.Settings  
> An outage occurs during this change.

Is there any complete way to zdp Aurora MySQL DB?

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