DocumentDB

1. What is AWS DocumentDB?

• Fully managed NoSQL document database service

• Compatible with MongoDB 3.6, 4.0, 5.0 APIs

• Designed for JSON-like document storage and queries

• Handles scaling, backups, patching, and high availability automatically

• Ideal for apps needing flexible, semi-structured data models

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2. Key Features

Feature	Description
MongoDB compatible	Supports MongoDB drivers and tools
Multi-AZ replication	Uses replicas for high availability
Automatic backups	Continuous backups with point-in-time restore
Scalable read replicas	Up to 15 read replicas
Encryption	Data encrypted at rest and in transit
VPC-only access	Runs inside your private VPC for security

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3. Basic Architecture

• Cluster: One primary node + multiple read replicas

• Storage: Distributed, fault-tolerant, automatically scaled

• Compute: Managed instance types (similar to EC2)

• Network: Runs inside your VPC, accessible via security groups

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4. Use Cases

• Content management systems

• Catalogs and product data

• Mobile apps with dynamic schemas

• Real-time analytics on JSON data

• Any app using MongoDB API that wants managed service

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5. Supported Operations

• CRUD operations using MongoDB shell or drivers

• Aggregation pipelines

• Indexing on fields

• Change streams (via some MongoDB compatibility)

• Transactions support on clusters (limited compared to native MongoDB)

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6. Provisioning DocumentDB

Via AWS Console:

1. Go to Amazon DocumentDB service

2. Click Create Cluster

3. Configure:

   • Cluster identifier

   • Instance class (e.g., db.r6g.large)

   • Number of instances (primary + replicas)

   • VPC and subnet group

   • Security group for access

4. Enable backups and encryption as needed

5. Create cluster

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7. Connecting to DocumentDB

• Use standard MongoDB drivers and connection strings

• Connection string example:

mongodb://username:password@docdb-cluster.cluster-xxxxxx.us-east-1.docdb.amazonaws.com:27017/?ssl=true&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false

• Requires SSL connection (DocumentDB uses TLS)

• Use AWS Certificate Bundle or download the root CA for SSL verification

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8. Replication in DocumentDB

• Supports asynchronous replication across multiple Availability Zones for high availability

• One primary instance handles writes

• Multiple read replicas serve reads, offloading the primary

• Failover happens automatically within seconds if primary fails

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9. Backups and Restore

• Automatic backups enabled by default with 7-day retention (configurable up to 35 days)

• Point-in-time recovery (PITR) to any second within backup retention

• Manual snapshots possible

• Snapshots can be shared and copied across regions

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10. Scaling

• Scale up by increasing instance size or adding replicas

• Storage is auto-scaling (starts at 10GB, can grow to 64TB)

• Use read replicas to improve read throughput

• No sharding support — single cluster only

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11. Security

• Runs in your VPC, controlled by security groups

• Supports IAM authentication (optional)

• Data encrypted at rest with KMS

• TLS encrypted in transit

• Fine-grained access control via MongoDB users and roles

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12. Monitoring

• Integrated with CloudWatch (CPU, memory, connections, disk usage)

• Enhanced Monitoring with OS metrics

• Alerts and alarms via CloudWatch Events

• Integration with AWS CloudTrail for auditing API calls

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13. Terraform Example

resource "aws_docdb_cluster" "example" {
  cluster_identifier      = "my-docdb-cluster"
  master_username         = "docdbuser"
  master_password         = "SuperSecret1234"
  backup_retention_period = 7
  preferred_backup_window = "07:00-09:00"
  vpc_security_group_ids  = [aws_security_group.docdb_sg.id]
  db_subnet_group_name    = aws_docdb_subnet_group.example.name
  storage_encrypted       = true
  skip_final_snapshot     = true
}

resource "aws_docdb_cluster_instance" "example" {
  count              = 2
  identifier         = "my-docdb-instance-${count.index}"
  cluster_identifier = aws_docdb_cluster.example.id
  instance_class     = "db.r5.large"
  engine             = "docdb"
  engine_version     = "4.0.0"
  publicly_accessible = false
}

resource "aws_docdb_subnet_group" "example" {
  name       = "example-subnet-group"
  subnet_ids = [aws_subnet.subnet1.id, aws_subnet.subnet2.id]
}

resource "aws_security_group" "docdb_sg" {
  name        = "docdb-security-group"
  description = "Allow inbound access on 27017"
  vpc_id      = aws_vpc.main.id

  ingress {
    from_port   = 27017
    to_port     = 27017
    protocol    = "tcp"
    cidr_blocks = ["10.0.0.0/16"]  # your app's CIDR
  }

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

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14. Limitations

Limitation	Notes
No support for MongoDB sharding	Scale by read replicas only
Some MongoDB features missing	Change streams, transactions limited
No support for direct on-premise access	Only via VPC or VPN
No free tier	Costs can add up with scaling

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15. Summary

Topic	AWS DocumentDB
Type	Managed MongoDB-compatible NoSQL
Scalability	Auto storage, read replicas
Replication	Multi-AZ async replication
Backup	Continuous + snapshots
Security	VPC, KMS encryption, IAM auth
Use Case	JSON doc DB, flexible schema apps

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