Amazon DocumentDB Cost Estimator: Size Your Workload in Minutes - Part 1
Amazon DocumentDB (with MongoDB compatibility) is a serverless, fully managed native JSON document database that makes it straightforward and cost effective to operate critical document workloads at virtually any scale without managing infrastructure.
The Amazon DocumentDB Cost Estimator is a web-based calculator built by the Amazon DocumentDB Specialist SA team and now maintained by Improving, that accepts your workload characteristics and produces instance recommendations, storage estimates, I/O projections, and real-time pricing breakdowns. Pricing comes from the AWS Pricing and Savings Plans APIs, so the numbers reflect current rates for the region you select.
The calculator provides two modes for sizing your workload:
- Basic mode — A quick single-collection form for fast estimates. Enter your workload characteristics for one collection and get a recommendation in seconds. Ideal when you're evaluating a new project or need a quick sanity check on instance sizing.
- Advanced mode — A CSV upload path for real world multi-collection environments. Upload metadata for dozens (or hundreds) of collections at once, and the calculator aggregates everything into a single cluster recommendation. Ideal for migration planning or production workloads spanning multiple collections.
This article is Part 1 of a two-part series. In this post, you learn how to use Basic mode to size a single collection and interpret the results. Part 2 covers Advanced mode - including how to prepare your CSV, upload multi-collection workloads to get sizing and pricing recommendations.
Size a Single Collection Using Basic Mode
Basic mode is the fastest way to a get sizing and pricing recommendation. The example below sizes a realistic workload: 10 million user-profile documents at ~2 KB each, with moderate read/write traffic.
Step 1: Enter Workload Characteristics
Enter the following workload characteristics into the form. Every field includes a tooltip explaining what it means and how to pick a value.
Step 2: Configure Cluster Options, Migration Source & Pricing Model
Next, configure the cluster options . These choices shape the recommendation as much as the workload data itself:
- MongoDB migration — Enable this if you're migrating from MongoDB. It adjusts index-size estimates.
- Serverless comparison — Adds a serverless pricing card so you can see break-even analysis side by side with provisioned.
- Region — Pick the region where you plan to deploy. Instance, storage, and I/O rates vary by region, so selecting the region where you plan to deploy ensures the cost estimate is accurate.
- Backup retention — select you backup retention period. The minimum is 1 day, which comes at no extra charge.
- Availability — Choose the availability tier that matches your SLA requirements.
Step 3: Generate the Sizing and Pricing Recommendation
Choose Calculate to generate the recommendation.
Interpreting the Recommendations
The results page is layered so you can see sizing and pricing recommendations. Depending on your workload characteristics, you'll see up to three cards as above:
Memory-Based Recommendation
This is usually the primary card. It shows the recommended instance type, node count (writer + read replicas), storage, I/O, and a full monthly cost breakdown. Memory sizing matters most because when your working set doesn't fit in RAM, queries hit disk and latency spikes.
Operations-Based Recommendation
This card appears based on your read/write volume. When both cards show up, a banner explains exactly why they differ so you know which dimension is driving the sizing.
When both cards appear, an explanation banner tells you exactly why they differ, so you can understand which dimension is driving the sizing.
Serverless Comparison
The key number here is the break-even utilization percentage. The calculator converts your memory needs into DocumentDB Capacity Units (DCUs) and tells you the utilization level where serverless and provisioned cost the same. Below that threshold, serverless wins; above it, provisioned is cheaper.
Savings Plans Information
Shows 1-year commitment options with the discounted instance cost, total monthly cost, and both dollar and percentage savings versus on-demand pricing.
Disclaimer : This is not an official AWS product and is provided for reference purposes only. All estimates are approximations and should be validated through performance testing.
What's Next — Part 2: Advanced Mode
In Part 2 of this series, you learn how to use Advanced mode to size multi-collection workloads. This includes:
- Preparing your CSV with collection-level metadata
- Using the Amazon DocumentDB Sizing Tool to pull stats from a running MongoDB cluster
- Uploading and validating multi-collection data and get sizing and pricing recommendations
Want to learn about Amazon DocumentDB (with MongoDB compatibility) ? Join the NoSQL Launchpad in Builder Center — that's where AWS NoSQL specialists hang out, share war stories like the ones in this series, and help teams work through exactly these kinds of problems before their big day.
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