Overview

There are yearly/monthly and pay-per-use billing modes. Each one has different advantages and disadvantages.

Yearly/Monthly is a prepaid billing mode. You pay in advance for a subscription term, and in exchange, you get a discounted rate. The longer the subscription term, the bigger the discount. Yearly/Monthly billing is a good option for long-term, stable services.
Pay-per-use is a postpaid billing mode. You pay as you go and just pay for what you use. The DB instance usage is calculated by the second but billed every hour. There are no wasted resources.

Table 1 lists the differences between the two billing modes.

**Table 1** Differences between billing modes
Billing Mode	Yearly/Monthly	Pay-per-use
Payment	Prepaid	Postpaid
Billing Method	Billed by the subscription term you purchase	Calculated by the second but billed every hour
Billed Items	Instance classes (vCPUs and memory), storage space, backup space, cross-region backup, EIPs, Monitoring by Seconds (for RDS for MySQL only), database proxies (for RDS for MySQL only), images (for RDS for SQL Server only), and deployment in Dedicated Computing Cluster (DCC).	Instance classes (vCPUs and memory), storage space, backup space, cross-region backup, EIPs, Monitoring by Seconds (for RDS for MySQL only), database proxies (for RDS for MySQL only), images (for RDS for SQL Server only), and deployment in Dedicated Computing Cluster (DCC).
Changing the Billing Mode	Yearly/Monthly can be changed to pay-per-use. The change takes effect only after the yearly/monthly subscription expires. For details, see Yearly/Monthly to Pay-per-Use.	Pay-per-use can be changed to yearly/monthly. For details, see Pay-per-Use to Yearly/Monthly.
Changing the instance class	Supported	Supported
Application Scenarios	Recommended for resources expected to be in use long-term. A cost-effective option for scenarios where the resource usage duration is predictable.	Recommended when the resource demands are likely to fluctuate and you want more flexibility.