With Serverless v2, the hourly cost is somewhere like 12-20 cents per ACU per hour, depending on the AWS Region. You can check the price for each combination of AWS Region and Aurora database engine here: https://aws.amazon.com/rds/aurora/pricing/ Let's consider us-east-1, which (as of January 2024) is 12 cents per ACU per hour. The minimum for Serverless v2 is 0.5 ACUs, so 6 cents / hour. A typical month has 720 hours (30 days) or 744 (31 days). So if you set minimum capacity to 0.5 ACUs, leave the cluster idle, and nothing unexpected happens, best case is roughly $43-45 per month for instance charges. Plus whatever usage-based charges for storage, I/O, and there are some other optional features that could result in charges. (That's why you would go through the exercise with the pricing calculator.) What could interfere with the best case? Turning on memory-consuming or CPU-consuming features could prevent the idle cluster from scaling down to 0.5 ACUs. Something like Performance Insights (minimum 2 ACUs) or global database (minimum 8 ACUs). Cleanup operations like PostgreSQL vacuum could run and cause scaling up when you think the database should be idle. What actions could you take to make the best case even better? Do "stop cluster" overnight or other long periods when you don't need to use the database. If you need to add reader instances to the cluster to test out multi-AZ usage (read/write splitting etc.), delete the reader instances when they're not needed. Have cron jobs to run stop-db-cluster, modify-db-cluster, etc. to put things into a cheaper state during overnight periods if you forget to do it at the end of the day.

To estimate the cost of a cross-region headless cluster using AWS Aurora Global Database in the AWS Pricing Calculator, you’ll need to manually configure the components since the calculator doesn’t provide a direct “headless cluster” option. In a headless Aurora cluster, where no writer or reader instances are provisioned and only storage is used (for scenarios like DR or cross-region replication), you can focus on the storage and I/O costs. First, select Amazon Aurora in the calculator and configure the Global Database option. Then, for each region involved, specify the estimated amount of storage in GB under “Storage” (using Aurora’s default storage type, usually General Purpose SSD). You can also estimate the backup storage and I/O requests based on your expected usage. Make sure to set the instance count to zero or deselect instances if possible to simulate a headless configuration. While the calculator may still require at least one instance to be configured for some settings, you can use a minimal instance temporarily just to calculate base storage and I/O, and then exclude instance pricing manually in your internal cost estimates. Additionally, don’t forget to account for cross-region data transfer costs, which are incurred when replication traffic flows between primary and secondary clusters

what does “unrealistically low” mean for you? 10$? 100$? 3789$? this question is the mother of “it depends”.

Hey Kyle, Here's what is mentioned in the Serverless documentation[1]: If your provisioned workload has memory requirements that are too high for small DB instance classes such as T3 or T4g, choose a minimum ACU setting that provides memory comparable to an R5 or R6g DB instance. In particular, we recommend the following minimum capacity for use with the specified features (these recommendations are subject to change): Performance Insights – 2 ACUs Aurora global databases – 8 ACUs (applies only to the primary AWS Region) Now, I can tell you that Performance Insights is definitely wanting 2 ACU/4gb because you need extra RAM to store the performance_schema tables Performance Insights requires. The 8 ACU is precisely in line with the memory requirements for provisioned instances - the r5.large is 2 vCPU and 16gb, and 8 ACU is the same 16gb of RAM. So they're asking roughly the same specifications. They are recommendations, not absolute rules, so you can go lower, though it does risk out-of-memory errors, and problems with slower than expected replication. It's important to remember to ask how much money might be saved, and how much a crash or restart might affect your application. If it's a new application, still being tested, you can probably afford a lot of scaling up (then back down), and/or the occasional crash. If it's for production, you'd want to measure the cost savings versus the costs of a crash or OOM error. In regards to the AWS pricing calculator please know that the charges for Aurora Serverless v2 capacity are measured in terms of ACU-hours. This is calculated by the average # of ACU's used per hour. For example, if on average every hour you use 4 ACUs for 30 minutes and 2 ACUs for the other 30 minutes each hour would be 3 ACU's. How you calculate this estimate is entirely based on your workload and how often it scales up/down ACUs. Please take a look at the following documentation for more examples on how this estimation process works [2]. Please note in addition to ACU’s used per hour you will be charged for storage rate and I/O rate. For Aurora Standard in US-East-1 you are charged $0.10 per GB-month and $0.20 per 1 million requests. For more information on these prices please view here [3]. Also if you leave the instance running it will continue to use the minimum ACU value that you configured for this cluster. As per Doc [4] “Aurora Serverless v2 writers and readers don't scale all the way down to zero ACUs. Idle Aurora Serverless v2 writers and readers can scale down to the minimum ACU value that you specified for the cluster.” **References:** [1]https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-serverless-v2.setting-capacity.html#aurora-serverless-v2.min_capacity_considerations [2]Aurora Pricing Examples: https://aws.amazon.com/rds/aurora/pricing/#:~:text=Japanese%20Consumption%20Tax.-,Aurora%20pricing%20examples,-The%20following%20examples [3]Amazon Aurora Pricing: https://aws.amazon.com/rds/aurora/pricing/ [4]https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-serverless-v2.how-it-works.html#aurora-serverless-v2.how-it-works.scaling

Hello, I asked AWS about this and it’s complicated to evaluate. 1 ACU is about 2GB of memory and corresponding CPU. You can track CPU on Cloudwatch but the real memory consumption is a calculated metric based on your engine. My client used aurora MySQL, I tried to compare all the instances of there clusters to ACU (based on the memory of the instances). For the usage trend I took the CPU usage graph even if it’s not totally relevant. It costs three times the price. Our strategy is to used it for the non productions workloads in a near future but not in production. If you don’t have a significant usage spike on your workload, aurora serverless is not the answer I think.