My Cloud Cost Horror Story (AWS)
I left an RDS t3.medium instance running for a side project, and it ended up costing me 200,000 KRW a month. There's barely any traffic, so why is it so expensive? I didn't even set up a budget alert, so I only found out way too late. How does everyone else manage their cloud costs?
4 answers
I've had a similar experience. I left a development RDS running without using a reserved instance, and ended up with a bill of 150,000 won in one month. Turns out the backup retention period was set to the default of 7 days, which caused storage costs to skyrocket. Now I've downgraded to t3.small and created a script to only turn it on when needed. Make sure to set up budget alerts.
Wow, 200,000 won really hurts... I'm also using Lambda and DynamoDB for my side project, and luckily serverless keeps costs almost nonexistent. RDS is convenient, but if traffic is low, consider Aurora Serverless or Lightsail. Definitely set up budget alerts this time—you can do it for free with AWS Budgets!
A t3.medium on-demand instance costs about $0.05 per hour, so if you run it 24/7, it comes out to around 30,000–40,000 KRW per month. If you're seeing 200,000 KRW, it might be due to reserved instances, storage costs, or data transfer fees piling up. Make sure to break it down by item using the AWS Cost Explorer. I've been hit by a surprise bill before too—turns out my EBS snapshots had been accumulating.
Have you enabled Multi-AZ on your RDS? A t3.medium doesn't usually cost that much by default, but costs can spike significantly if you use Multi-AZ or provisioned IOPS storage. I didn't know this at first either and was shocked after setting it up. For cost optimization tips, I recommend finding the right instance size and leveraging reserved instances.