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I have a master db in one region.. and I want to create a read replica of it in another region just for disaster recovery practices.

I do not want it to be that costly, but I want the replication to work. My current master db has db.t2.medium. My question is:

  • What type should I keep for my read replica? Is db.t2.small fine for my replica?
devgirl
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    Its impossible to answer. Depends on you load and how "busy" is your primary db. Only you know this. – Marcin Nov 23 '20 at 23:04
  • @Marcin yes that I understand, thanks! However, is it possible that I keep a lesser storage type for a read replica than the master? It wont effect replication right? – devgirl Nov 24 '20 at 02:13

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It should not have much effect as read replica (RR) replication is asynchronous:

Amazon RDS then uses the asynchronous replication method for the DB engine to update the read replica whenever there is a change to the primary DB instance.

This means that your RR will be always lagging behind the master. For exactly how much, it depends on your setup. Thus you should monitor the lag as shown in Monitoring read replication. This is needed, because you may find that the lag is unacceptably large for the RR to be useful for DR purposes (i.e. large RPO).

Marcin
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