RDS Read Instance for Analytics Work. Would this cause performance issues on the DB?

Question

If an RDS has a writer and a reader instance. If I then want to complete Analytics work by connecting to the Reader instance. Given that both instances connect to the same DB. Is there a potential to cause performance issues on the DB? Need to think of a worse case scenario where our DA would affect the performance of the Database (which most of the users connect to).

Aws lets you have up to 15 reader instances (with mysql) and we want to start more analytics work. Creating a completely separate Analytics DB would cost more.

shibata · Accepted Answer

Read replica in RDS is realized based on the replication function of MySQL.
This is achieved by transferring the binary log of the write instance to the reader instance and reproducing it on the reader instance.

In other words, since the read instance exists separately, including the disk, it is not considered to affect the write instance.

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_ReadRepl.html
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_MySQL.Replication.ReadReplicas.html

Gareth_E · Answer

Agreed that queries on the read replica will not impact the primary database server, however there is a small risk that if your queries on the read replica max out the CPU that the replication process will slow down in writing updates to the read replica and replication lag will increase (the amount of time the replica is behind the primary database).

If you're using MySQL, have you considered migrating to Amazon Aurora MySQL compatible? Aurora separates the compute and the storage, and the primary and read replica's all reference the same underlying logical storage, so you don't have the issue of heavy reads on a read replica increasing replication latency. See: https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Aurora.Replication.html

Also, Aurora includes an optional feature (Parallel Query) that speeds up analytical queries by pushing down some of the query processing to the storage layer. See: https://aws.amazon.com/rds/aurora/parallel-query/.

Because of these things, your may benefit significantly by migrating to Aurora.

RDS Read Instance for Analytics Work. Would this cause performance issues on the DB?

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