Amazon DocumentDB (with MongoDB compatibility) pricing

Amazon DocumentDB (with MongoDB compatibility) is a fully managed document database service that supports MongoDB workloads. With Amazon DocumentDB, you only pay for what you use, and there are no upfront costs. Amazon DocumentDB pricing has four dimensions:

1. On-demand instances: The amount of compute instances for a cluster (pricing per hour)
2. Database I/O: The amount of I/O used when reading and writing data to your cluster’s storage volume (pricing per million I/Os).
3. Database storage: The amount of data stored in your cluster's storage volume (pricing per GB/month).
4. Backup storage: The amount of backup storage used in excess of your cluster’s database storage usage (pricing per GB/month).

Your total database spend depends on the storage configuration of your database cluster. You can choose between two options:

1. Amazon DocumentDB Standard (pay-per-use I/O model): It is designed for customers with low to moderate I/O consumption. If you expect your I/O costs to be less than 25% of your database cluster spend, this choice might be ideal for you. In standard configuration, you are billed across all four dimensions: instance, database I/O, database storage, and backup storage. This option  offers adaptability to suit your dynamic I/O needs. 
2. Amazon DocumentDB I/O-Optimized (I/O included model): Amazon DocumentDB I/O-Optimized is designed for customers who prioritize price predictability or have I/O intensive applications. If you expect your I/O costs to exceed 25% of your database cluster spend, this option offers enhanced price performance. With Amazon DocumentDB I/O-Optimized storage configuration, you are billed across three dimensions: instance, database storage, and backup storage. You won't be charged based on I/O operations, ensuring predictable costs each billing cycle. 
   

On-Demand Instances let you pay by the hour with no long-term commitments or upfront fees. This frees you from the cost and complexity of planning and purchasing database capacity ahead of your needs. On-Demand pricing lets you pay as you go and is ideal for development, test and other short-lived workloads.

Pricing is per instance-hour consumed, from the time an instance is launched until it is stopped or deleted. Partial instance hours are billed in one-second increments, with a 10-minute minimum charge following a billable status change such as creating, modifying, or deleting an instance.

Instance pricing applies to both primary instances, used for read-write workloads, and Amazon DocumentDB replicas, used to scale reads and enhance failover. Amazon DocumentDB uses Multi-AZ architecture to failover to one of your replicas if an outage occurs. The cost of Multi-AZ deployments is simply the cost of the primary instance plus the cost of each Amazon DocumentDB replica. To maximize availability, we recommend placing at least one replica in a different Availability Zone from the primary instance.

Amazon DocumentDB T3 and T4g medium instances run in Unlimited mode, which means that you will be charged if your average CPU utilization over a rolling 24-hour period exceeds the baseline of the instance. CPU Credits are charged at ¥0.616 per vCPU-Hour. The CPU Credit pricing is the same for all T3 and T4g instance sizes across all regions. For more information on how unlimited burstable performance instances work and how it is priced, see Unlimited mode concepts.

Storage consumed by your Amazon DocumentDB cluster is billed per GB-month. Billable storage includes your data, indexes, and change stream data. I/Os consumed are billed per million I/O requests. Reads and writes to your storage volume count as billable I/O requests, including reads and writes from features like change streams and TTL indexes. You pay only for the storage and IOs that your Amazon DocumentDB cluster consumes, and do not need to provision these resources in advance.

Backup storage for an Amazon DocumentDB cluster is the storage associated with your automated cluster backups and any manual cluster snapshots. Increasing your backup retention period or taking manual cluster snapshots increases the backup storage consumed.

• Backup storage is allocated by region. Total backup storage space is equivalent to the sum of the storage for all backups in that region.
• Copying a snapshot to another region increases allocated backup storage in the destination region.
• There is no additional charge for backup storage of up to 100% of your total Amazon DocumentDB cluster storage for a region. There is also no additional charge for backup storage if your backup retention period is 1 day and you do not have any manual snapshots beyond the backup retention period. Backup storage beyond this amount and manual snapshots retained outside of the backup retention period, whether your cluster is active or has been deleted, are billed at storage rates in the table below.
  

The pricing below is based on data transferred “in” and “out” of Amazon DocumentDB

• Data transferred between Amazon DocumentDB and Amazon EC2 Instances in the same Availability Zone is free.
• Data transferred between Availability Zones for replication of Multi-AZ deployments is free.
• Amazon DocumentDB database instances outside VPC: For data transferred between an Amazon EC2 instance and Amazon DocumentDB database instance in different Availability Zones of the same Region, there is no Data Transfer charge for traffic in or out of the Amazon DocumentDB database instance. You are only charged for the Data Transfer in or out of the Amazon EC2 instance, and standard Amazon EC2 Regional Data Transfer charges apply.
• Amazon DocumentDB database instances inside VPC: For data transferred between an Amazon EC2 instance and Amazon DocumentDB database instance in different Availability Zones of the same Region, Amazon EC2 Regional Data Transfer charges apply on both sides of transfer.