Estimate an Amazon DocumentDB bill across instance hours, cluster storage, I/O requests and backup beyond the free allowance.
DocumentDB uses the same decoupled architecture as Aurora: one shared cluster volume billed once no matter how many instances read it, plus a per-request I/O charge and instance-hours for each node. Backup storage up to the size of the cluster volume is free, so only the retention window and change rate that push you past that size cost anything. Every rate is an editable input with a realistic us-east-1 default — confirm current prices with AWS for your region. Because storage is shared, adding a replica to DocumentDB only adds instance-hours and read I/O — which makes the compute share of the bill the number that tells you whether to scale out or scale up.
DocumentDB Cost
monthly = instances × hourly × hours + GB × storage rate + I/O millions × I/O rate + max(0, backup GB − cluster GB) × backup rate.
monthly = instances × hourly × hours + GB × storage rate + I/O millions × I/O rate + max(0, backup GB − cluster GB) × backup rate. DocumentDB uses the same decoupled architecture as Aurora: one shared cluster volume billed once no matter how many instances read it, plus a per-request I/O charge and instance-hours for each node. Backup storage up to the size of the cluster volume is free, so only the retention window and change rate that push you past that size cost anything. Every rate is an editable input with a realistic us-east-1 default — confirm current prices with AWS for your region.
Because storage is shared, adding a replica to DocumentDB only adds instance-hours and read I/O — which makes the compute share of the bill the number that tells you whether to scale out or scale up.
This calculator takes 9 inputs: Instances in the cluster, Instance price, Billed hours per month, Cluster storage in use, Storage price, I/O requests per month, I/O price, Backup storage held, Backup storage price. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
They are realistic us-east-1 on-demand defaults and nothing more. DocumentDB rates vary by region and instance family, so confirm each one against the AWS DocumentDB pricing page for your region.