Merging AWS RDS Databases: (when) should we do it?

Prologue

source: https://aminoapps.com/c/cartoon/page/blog/roastin-cat-dog/r0jU_euxmWmY1MqnXqmlgz41GawgXvX

Evaluating the Merge

RDS Storage limits

SELECT 
table_schema 'Database Name',
ROUND(SUM(data_length + index_length) / (1024 * 1024), 1) 'DB Size in MB'
FROM
information_schema.tables
GROUP BY table_schema;
SHOW BINARY LOGS;

RDS Instance Performance

RDS IOPS (I/O operations Per Second)

RDS Instance Type

source: https://www.furaffinity.net/view/14338513/

Max DB Connections Limit

source: https://www.tyro.com/blog/eftpos-advantages-disadvantages-need-one

What we’ll gain?

Utilize the RDS instance resources better and save money.

Query both databases at once

We can get rid of the additional infrastructure

Read-replication, auto-scaling and backups are not affected.

What we’ll lose?

Are we violating software engineering concepts?

Exceeding the EBS size limit

Single point of failure!

Code/design changes.

Monitoring will be hard(er)

How to merge?

Summary

If you want to change the world, start it yourself.