Here is where most financial surprises live. The calculator asks for
AWS DocumentDB is not cheap, but it is predictable. The pricing calculator is your only defense against I/O shock. Use the replicas slider carefully, respect the I/O rate, and always— always —model the reserved instance discount. aws documentdb pricing calculator
| Pitfall | Calculator Fix | | :--- | :--- | | | The calculator has a "Data Transfer" tab. If you query DocumentDB from EC2 in different AZs, you pay cross-AZ fees. Add those here. | | Assuming 100% Utilization | The calculator defaults to "Always On" (730 hours/month). For dev environments that shut down at night, use the "Partial month" toggle. | | Mixing Instance Families | Your primary can be r5.large but your read replica can be r5.xlarge . The calculator allows asymmetric clusters. Use it. | Here is where most financial surprises live
"I need to retain 30 days of change logs." Enter 2,000GB. The calculator adds that cost. Most users forget this, then cry when the bill arrives. Use the replicas slider carefully, respect the I/O
Step 4: Estimate Storage and I/OThis is often the hardest part to predict. Look at your current MongoDB metrics or application logs to estimate: Total storage: How many GBs of JSON data will you store? I/O Rate: How many read/write operations occur per second?
DocumentDB utilizes a cluster volume, which is a single, logical volume spanning multiple Availability Zones (AZs).