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Amazon DocumentDB Limits

This topic describes the resource limits and naming constraints for Amazon DocumentDB (with MongoDB compatibility).

For certain management features, Amazon DocumentDB uses operational technology that is shared with Amazon Relational Database Service (Amazon RDS) and Amazon Neptune.

Supported Instance Types

Amazon DocumentDB supports on-demand instances and the following instance types:

• Memory Optimized:

  • Current Generation:

    R5 instance types: db.r5.large, db.r5.2xlarge, db.r5.4xlarge, db.r5.12xlarge, db.r5.24xlarge.

    R4 instance types: db.r4.large, db.r4.2xlarge, db.r4.4xlarge, db.r4.8xlarge, db.r4.16xlarge.

For more information on the supported instance types and their specifications, see Instance Class Specifications.

Supported Regions

Amazon DocumentDB is available in the following AWS regions:

Region Name	Region	Availability Zones (compute)
US East (Ohio)	us-east-2	3
US East (N. Virginia)	us-east-1	6
US West (Oregon)	us-west-2	4
Asia Pacific (Seoul)	ap-northeast-2	3
Asia Pacific (Sydney)	ap-southeast-2	2
Asia Pacific (Tokyo)	ap-northeast-1	3
EU (Frankfurt)	eu-central-1	3
EU (Ireland)	eu-west-1	3
EU (London)	eu-west-2	3

Regional Limits

For certain management features, Amazon DocumentDB uses operational technology that is shared with Amazon Relational Database Service (Amazon RDS) and Amazon Neptune. The following table contains regional limits that are shared among Amazon DocumentDB, Amazon RDS, and Neptune.

The following limits are per AWS account per region.

Resource	Default Limit
Clusters	40
Instances	40
Event subscriptions	20
Manual cluster snapshots	100
Cluster parameter groups	50
Read replicas per cluster	15
VPC security groups per instance	5
Subnet groups	50
Subnets per subnet group	20
Tags per resource	50

You can take the following steps to request an increase for limits. These increases are not granted immediately, so it may take a couple of days for your increase to become effective.

To request a limit increase

1. Open the AWS Support Center page at https://console.aws.amazon.com/support/home, sign in if necessary, and choose Create case.

2. For Regarding, choose Service Limit Increase.

3. For Limit type, choose RDS from the list.

4. Complete the form. If this request is urgent, choose Phone as the method of contact instead of Web.

5. Choose Submit.

Aggregation Limits

The following table describes aggregation limits in Amazon DocumentDB.

Resource	Default Limit
Maximum number of supported stages	500

Cluster Limits

The following table describes Amazon DocumentDB cluster limits.

Resource	Limit
Cluster size (sum of all collections and indexes)	64 TB
Database size (sum of all databases can't exceed cluster limit)	64 TB
Collection size (sum of all collections can't exceed cluster limit) – does not include the index size	32 TB
Collections per cluster	100,000
Document size	16 MB
Document nesting depth	100 levels
Indexes per collection	64
Index key size (for arrays, the entire array must be less than 2,048 bytes)	2,048 bytes
Keys in a compound index	32
Number of users per cluster	100
Maximum number of writes in a single batch command	100,000

Instance Limits

The following table describes Amazon DocumentDB limits per instance.

Resource	Limit
Number of concurrent connections by instance type	db.r5.large – 1,100 db.r4.large – 1,100
	db.r5.xlarge – 2,700 db.r4.xlarge – 2,700
	db.r5.2xlarge – 4,500 db.r4.2xlarge – 4,500
	db.r5.4xlarge – 4,500 db.r4.4xlarge – 4,500
	db.r4.8xlarge – 4,500
	db.r5.12xlarge – 4,500
	db.r4.16xlarge – 4,500
	db.r5.24xlarge – 4,500
Maximum number of open cursors per instance	450

Naming Constraints

The following table describes naming constraints in Amazon DocumentDB.

Resource	Default Limit
Cluster identifier	Length is [1–63] letters, numbers, or hyphens. First character must be a letter. Cannot end with a hyphen or contain two consecutive hyphens. Must be unique for all clusters (across Amazon RDS, Amazon Neptune, and Amazon DocumentDB) per AWS account, per Region.
Instance identifier	Length is [1–63] letters, numbers, or hyphens First character must be a letter Cannot end with a hyphen or contain two consecutive hyphens Must be unique for all instances (across Amazon RDS, Amazon Neptune, and Amazon DocumentDB) per AWS account, per Region.
Master user name	Length is [1-63] alphanumeric characters. First character must be a letter. Cannot be a word reserved by the database engine.
Master password	Length is [8-100] printable ASCII characters. Can use any printable ASCII characters except for the following: / (forward slash) " (double quotation mark) @ (at symbol)
Parameter group name	Length is [1–255] alphanumeric characters. First character must be a letter. Cannot end with a hyphen or contain two consecutive hyphens.
Database name: <db>	Length is [1–63] characters.
Collection name: <col>	Length is [1–57] characters.
Fully qualified collection name: <db>.<col>	Length is [3–120] characters.
Index name: <col>$<index>	Length is [3–63] characters.
Fully qualified index name: <db>.<col>.$<index>	Length is [6–127] characters.

TTL Constraints

Deletes from a TTL index are not guaranteed within a specific timeframe and are best effort. Factors like instance resource utilization, document size, and overall throughput can affect the timing of a TTL delete.