Amazon DocumentDB Cheat Sheet

• Fully managed document database service designed to be fast, scalable, and highly available.
• Data is stored in JSON-like documents.
• Compatible with MongoDb.
• Flexible schema and indexing.
• Commonly used for content management, user profiles, and real-time big data.

How it Works

• An Amazon DocumentDB cluster decouples storage and compute.
• A cluster consists of Cluster volume and Instances
  • Cluster volume refers to the storage layer that spans multiple Availability Zones. Each Availability Zone has a copy of the cluster data.
  • Instances refers to the compute layer. It provides the processing power needed for the database to write data to, and read data from, the cluster volume. 
• Amazon DocumentDB Endpoints
  • Cluster endpoint
    • Connects to cluster’s current primary instance.
    • Can be used for both read and write operations.

• • Reader endpoint
    • Connects to one of the available replicas of the cluster.
    • Use for read operations only.
    • If the cluster has more than one replica, the reader endpoint will direct each request to DocumentDB replicas.

• • Instance endpoint
    • Connects to a specific instance in the cluster.
    • Use for specialized workloads that will only affect specific replica instances.

Performance

• Provides millions of requests per second with millisecond latency and has twice the throughput of MongoDb.

Amazon DocumentDB Scaling

• The minimum storage is 10GB. The Amazon DocumentDB storage will automatically scale up to 64 TB in 10 GB increments without affecting performance.
• The Amazon DocumentDB cluster can be scaled by modifying the instance class for each instance in the cluster.
• You can create up to 15 Amazon DocumentDB replicas in the cluster.
• The replication lag is usually less than 100 milliseconds after the primary instance has written an update.

Amazon DocumentDB Reliability

• The cluster volume provides durability by maintaining six copies of all data across three Availability Zones.
• Amazon DocumentDB uses asynchronous replication to update the changes made to the primary instance to all of DocumentDB’s read replicas.
• In most cases, the DocumentDB’s restart time is less than a minute after a database crash.
• DocumentDB replicas can act as a failover target with no data loss.
• Supports automatic failover.
• Supports promotion priority within a cluster. Amazon DocumentDB will promote the replica with the highest priority tier to primary when the primary instance fails.
• To increase the cluster’s availability, create replicas in multiple Availability Zones. The Amazon DocumentDB will automatically include the replicas when selecting for a failover target in the event of an instance failure.

Backup And Restore

• Automated backups are always enabled.
• Supports Point-In-Time restoration, which can be up to 5 minutes in the past.
• You can restore from a cluster snapshot.
• Supports sharing of encrypted manual snapshots.
• Supports cross-region snapshot copying.

Amazon DocumentDB Security

• You can authenticate a connection to a DocumentDB database through standard MongoDb tools with Salted Challenge Response Authentication Mechanism (SCRAM).
• You can authenticate and authorize the use of DocumentDB management APIs through the use of IAM users, roles, and policies.
• Data in transit is encrypted using Transport Layer Security (TLS).
• Data at rest is encrypted using keys you manage through AWS KMS.
• Amazon DocumentDB supports role based access control ( RBAC ) with built-in roles to enforce the principle of least privileged access.

Amazon DocumentDB Pricing

• You are billed based on four categories
  • On-demand instances
    • Pricing per second with a 10-minute minimum
  • Database I/O
    • Pricing per million I/Os
  • Database Storage
    • Pricing per GB/month
  • Backup Storage
    • Pricing per GB/month

Amazon DocumentDB Limitations

• Amazon DocumentDB supports the Global Clusters feature which allows you to launch up to five read-only replicas.
• Encryption of an existing DocumentDB instance is not supported.
• Sharing of automatic DB snapshots to other accounts is not allowed. A workaround for this is to manually copy the snapshot from the automatic snapshot, then, copy the manual snapshot to another account.

Note: If you are studying for the AWS Certified Data Engineer Associate exam, we highly recommend that you take our AWS Certified Data Engineer Associate Practice Exams and read our Data Engineer Associate exam study guide.

Amazon DocumentDB Cheat Sheet References:

https://aws.amazon.com/documentdb/faqs/
https://aws.amazon.com/blogs/database/migrating-to-amazon-documentdb-with-the-online-method/