RDS Charge in 10 days for Free-Tier

Based on the information provided, it appears you're experiencing charges for your RDS instance despite believing you're using free tier options. There are a few key points to consider:

1. Instance Type: You mentioned using a db.t3.micro instance, which is eligible for the RDS free tier. However, the free tier has specific limitations:

   • 750 hours per month of db.t3.micro (or db.t2.micro, db.t4g.micro) Single-AZ instances
   • Running MySQL, MariaDB, or PostgreSQL databases
   • 20 GB of General Purpose SSD (gp2) storage

2. CPU Credits and Bursting: T3 instances use a CPU credit model. While the baseline performance is covered by the free tier, any usage above this baseline (bursting) can incur additional charges. This explains the vCPU-hour charges you're seeing.

3. Storage Type: Ensure you're using gp2 storage, as gp3 is not covered by the free tier.

4. Database Engine: Confirm you're using a supported free tier engine (MySQL, MariaDB, PostgreSQL, or SQL Server Express Edition). Note that Aurora is not included in the free tier.

5. Additional Resources: Check if you're using any resources not covered by the free tier, such as Multi-AZ deployment, additional storage, or certain types of backups.

6. Free Tier Duration: The AWS Free Tier typically lasts for 12 months from account creation. Verify that your account is still within this period.

To address your specific concerns:

• The 66.927 vCPU-Hours likely represent the total CPU time used, including both baseline and burst usage.
• The lack of free tier CPU credits from the start suggests there might be a configuration issue or you may be using a non-free tier eligible resource.

To resolve this:

1. Double-check all your RDS instance settings to ensure they align with free tier specifications.
2. Review your detailed billing statement to identify specific usage causing the charges.
3. Check your free tier usage status in the AWS Billing Console.
4. Consider setting up AWS Budgets to alert you when you're approaching or exceeding free tier limits.

If you believe you've been charged incorrectly despite adhering to all free tier requirements, it's advisable to contact AWS Support for clarification and potential adjustments.
Sources
Charged for AWS despite using Free tier | AWS re:Post
RDS Free Tier Charge | AWS re:Post
Getting charged for Free Tier | AWS re:Post
per vCPU-Hour of T3 CPU Credits | AWS re:Post
Abnormal Billing for the Free Resources | AWS re:Post

Hello.

db.t3.micro itself is an instance type eligible for the free tier, but there is a charge for burst credits.
Looking at the image metrics, the CPU usage rate is over 30%, so it is constantly bursting.
T3 instance types continue to burst in unlimited mode, so charges will be incurred if the CPU load increases.
Also, since db.t3.micro has specs that barely meet the hardware requirements of SQL Server, the CPU usage rate may exceed the baseline throughput even if it is only running.
https://aws.amazon.com/rds/instance-types/?nc1=h_ls

T3 instances accumulate CPU credits when a workload is operating below baseline threshold. Each earned CPU credit provides the T3 instance the opportunity to burst with the performance of a full CPU core for one minute when needed. Amazon RDS T3 instances are configured for Unlimited mode, which means they can burst beyond the baseline over a 24-hour window for an additional charge.

I think the following document will be helpful for explaining burst performance.
The following document is for EC2, but the idea is the same for RDS.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/burstable-credits-baseline-concepts.html

2nd screenshot is showing clearly that I didn't get any free-tier cpu credits even, so from the 1st minute onwards, i was being charged.

T3 instance types do not have CPU credits at startup.
After startup, CPU credits accumulate during the time when the throughput is below the baseline throughput.

The CPU Credit Specification should be set to Standard Mode to avoid unexpected charges from CPU bursting. This ensures the instance operates within its baseline CPU capacity and does not incur additional costs.