Thanks for the reply. We are using mysql 5.7.33 version. I am not able to see any option to modify the reserved instance. Can you guide me on that?

if i create a reserved instance with multi-az, is it possible to use it for an instance that does not use multi-az? Yes, but you'd be wasting half the money.. your can use a multi az rds to cover two single az rds of the same instance type and size, or even 4 single az instances at half the size. Ie 1 * m5.xlarge multi az = 4 * m5.large single az

u/philsw is correct, the fact it's a reserved instance is irrelevant.

With MySQL and Postgres you can only migrate one major version up, this means you have to upgrade in two steps:

5.5 -> 5.6

5.6 -> 5.7

That's correct, you specify the instance type that you want to purchase on that page, and once that's complete the instance will appear in the **Reserved Instances** section of the RDS Console. From here you configure storage, backups, etc. See the section *How To Purchase Reserved Instances* of https://aws.amazon.com/rds/reserved-instances/ Also be aware of the four important bulletpoints in the section *Important Notes about Purchases* at the foot of that page.

Create a Reserved RDS instance record that matches your current RDS instance's machine type. https://aws.amazon.com/rds/reserved-instances/

Thank you for your detailed questions about switching from RDS On-Demand to RDS Reserved Instances. I'll address each of your questions in order. q1) Yes, you are correct. You would need to go through the purchase process separately for each instance class. For your db.m5.large instances, you would specify 8 for the "Number of DB Instances" and complete that purchase. Then you would repeat the process for your 23 db.m6i.large instances, and again for your 3 db.m6i.xlarge instances. Each purchase would be specific to the instance class, deployment type (Multi-AZ in your case), and region (US East Ohio). q2) Reserved Instances are purchased for a fixed term of either one or three years. If you need an instance for 1 year and 6 months, you would benefit from the Reserved Instance pricing for the first year, and then pay On-Demand rates for the additional 6 months. If you only need the instance for 6-9 months, you would still be committed to paying for the full year of the Reserved Instance. In this case, it might be more cost-effective to use On-Demand instances if you're certain you won't need the instance for the full year. It's important to carefully consider your long-term needs when purchasing Reserved Instances. q3) After pressing "Next" on the initial page, you would typically see a summary of your selection and the associated costs. This would include details such as the total upfront cost (if any), the monthly recurring charges, and the effective hourly rate. You would have the opportunity to review these details and confirm your purchase. The exact steps may vary slightly, but generally, you would review the order summary, agree to the terms, and then finalize the purchase. Remember that while Reserved Instances offer significant savings for steady, long-term use, they also represent a commitment. Make sure you're confident in your long-term needs before making the purchase. Also, keep in mind that Reserved Instances are a billing construct and don't require any migration or changes to your existing instances - the discount is automatically applied to matching running instances in your account. **Sources** Amazon RDS Reserved Instances | Cloud Relational Database | Amazon Web Services On-Demand DB instances for Amazon RDS - Amazon Relational Database Service Purchasing reserved DB instances for Amazon RDS - Amazon Relational Database Service Reserved Instances

Think of it as purchasing a licence for one of your existing instances you already have rather than creating a new instance.