How to Use the DynamoDB Cost Calculator
Estimating your AWS bill can be complex. This dynamodb cost calculator helps you project monthly expenses for Amazon's NoSQL database based on your expected traffic and storage needs. To get an accurate estimate, you should have a baseline of your application's read and write patterns.
- Pricing Model
- Choose between 'On-Demand' (best for unpredictable traffic) or 'Provisioned' (best for steady-state workloads with predictable patterns).
- Monthly Reads/Writes
- In On-Demand mode, enter the total number of requests in millions. In Provisioned mode, enter the capacity units (RCU/WCU) you plan to reserve.
- Storage (GB)
- The total size of your table including metadata and indexed data.
- Data Egress (GB)
- The amount of data transferred out of the AWS region to the internet or other regions.
How DynamoDB Cost Is Calculated
DynamoDB pricing is primarily driven by three factors: throughput (reads/writes), storage, and data transfer. Our dynamodb cost calculator uses the following logic:
Total Cost = Throughput Cost + Storage Cost + Data Transfer Cost
- On-Demand Reads: Approximately $0.25 per million read request units.
- On-Demand Writes: Approximately $1.25 per million write request units.
- Provisioned RCU: Charged hourly at roughly $0.00013 per unit.
- Provisioned WCU: Charged hourly at roughly $0.00065 per unit.
- Storage: Standard rate is $0.25 per GB per month for the first 25GB (free tier excluded in this tool for simplicity).
Calculation Example
Scenario: A small web application using On-Demand pricing with 10 million reads, 2 million writes, and 50GB of data storage.
Step-by-step solution:
- Read Cost: 10 million * $0.25 = $2.50
- Write Cost: 2 million * $1.25 = $2.50
- Storage Cost: 50 GB * $0.25 = $12.50
- Transfer: Negligible for this example.
- Total: $2.50 + $2.50 + $12.50 = $17.50 per month
Common Questions
Is On-Demand always more expensive?
Not necessarily. While the "per-request" cost is higher than a fully utilized provisioned unit, On-Demand saves money if your traffic is "spiky" or idle for long periods. If your application utilization is below 15-20% of peak capacity, On-Demand is often cheaper than paying for unused provisioned capacity.
How does item size affect cost?
A single Read Request Unit (RRU) allows for 1 strongly consistent read (or 2 eventually consistent reads) of an item up to 4KB. If your items are 12KB, a single read will cost 3 RRUs. The dynamodb cost calculator assumes standard 4KB/1KB sizing; for larger items, you should scale your input numbers accordingly.
Are Global Tables included?
Global Tables add additional costs for replicated writes. Our current tool calculates a single-region deployment. For Global Tables, you typically double your write costs and add the replication data transfer fees between regions.