AWS Aurora Global Database vs. DynamoDB Global Tables

Aurora Global Database

• Aurora Global Database provides a relational database supporting MySQL and PostgreSQL.
• Aurora Global Database consists of one primary AWS Region where the data is mastered, and up to five read-only, secondary AWS Regions.
• Aurora cluster in the primary AWS Region performs both read and write operations. The clusters in the secondary Regions enable low-latency reads.
• Aurora replicates data to the secondary AWS Regions with a typical latency of under a second.
• Secondary clusters can be scaled independently by adding one or more DB instances (Aurora Replicas) to serve read-only workloads.
• Aurora Global Database uses dedicated infrastructure to replicate the data, leaving database resources available entirely to serve applications.
• Applications with a worldwide footprint can use reader instances in the secondary AWS Regions for low-latency reads.
• Typical cross-region replication takes less than 1 second.
• In case of a disaster or an outage, one of the clusters in a secondary AWS Region can be promoted to take full read/write workloads in under a minute.
• However, the process is not automatic. If the primary region becomes unavailable, you must manually remove a secondary region from an Aurora Global Database and promote it to take full reads and writes. You will also need to point the application to the newly promoted region.
• Architecture: Single-master, multi-reader (one primary region for writes, multiple secondary regions for reads).
• Consistency: Eventual consistency for cross-region reads.

DynamoDB Global Tables

• DynamoDB Global tables provide NoSQL database.
• DynamoDB Global tables provide a fully managed, multi-Region, and multi-active database that delivers fast, local, read and write performance for massively scaled, global applications.
• Global tables replicate the DynamoDB tables automatically across the choice of AWS Regions and enable reads and writes on all instances.
• DynamoDB global table consists of multiple replica tables (one per AWS Region). Every replica has the same table name and the same primary key schema. When an application writes data to a replica table in one Region, DynamoDB propagates the write to the other replica tables in the other AWS Regions automatically.
• Global tables enable the read and write of data locally providing single-digit-millisecond latency for the globally distributed application at any scale.
• DynamoDB Global tables are designed for 99.999% availability.
• DynamoDB Global tables enable the applications to stay highly available even in the unlikely event of isolation or degradation of an entire Region. Applications can redirect to a different Region and perform reads and writes against a different replica table.

DynamoDB Global Tables Consistency Modes

• DynamoDB Global Tables support two consistency modes:

Multi-Region Eventual Consistency (MREC) – Default

• Provides asynchronous replication with approximately 1-second replication latency for tables between two or more Regions.
• Multi-active: All replicas accept reads and writes.
• Conflict Resolution: Last Write Wins based on internal timestamp.
• RPO: Approximately 1 second (replication delay).
• Best for applications that can tolerate eventual consistency.

Multi-Region Strong Consistency (MRSC) – January 2025

• Announced at AWS re:Invent 2024 and generally available in January 2025.
• Provides synchronous replication across Regions.
• Strongly consistent reads always return the latest version of an item, irrespective of the Region.
• Zero RPO: Enables Recovery Point Objective of zero.
• Item changes are synchronously replicated to at least one other Region before write returns success.
• Deployment: Must be deployed in exactly three Regions (3 replicas OR 2 replicas + 1 witness).
• Regional Availability: Three Region sets (US, EU, AP) – cannot span Region sets.
• Trade-off: Higher write latency compared to MREC due to synchronous replication.
• Best for applications requiring global strong consistency and zero data loss.

Comparison Table

When to Choose Aurora Global Database

• Relational Data Model: Need SQL, complex queries, joins, and transactions.
• MySQL/PostgreSQL Compatibility: Existing applications using these databases.
• Single-Master Writes: Write operations centralized in one region is acceptable.
• Read-Heavy Workloads: Global read replicas for low-latency reads worldwide.
• Complex Analytics: Need advanced SQL features and reporting.
• Disaster Recovery: Can tolerate manual failover process (under 1 minute).

When to Choose DynamoDB Global Tables (MREC)

• NoSQL Data Model: Key-value or document data structure.
• Multi-Active Writes: Need to write to multiple regions simultaneously.
• Massive Scale: Require unlimited scalability with single-digit millisecond latency.
• High Availability: Need 99.999% availability with automatic failover.
• Eventual Consistency Acceptable: Can tolerate ~1 second replication delay.
• Serverless: Fully managed with no infrastructure management.

When to Choose DynamoDB Global Tables (MRSC)

• Zero RPO Required: Cannot tolerate any data loss.
• Global Strong Consistency: Need latest data across all regions immediately.
• Financial Applications: Banking, payments, trading systems.
• Inventory Management: Global inventory with strict consistency.
• Compliance Requirements: Regulations requiring zero data loss.
• Three-Region Deployment: Can deploy in exactly three regions within same region set (US, EU, or AP).

AWS Certification Exam Practice Questions

• Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
• AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
• AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
• Open to further feedback, discussion and correction.

1. A company needs to implement a relational database with a multi-region disaster recovery Recovery Point Objective (RPO) of 1 second and a Recovery Time Objective (RTO) of 1 minute. Which AWS solution can achieve this?
   1. Amazon Aurora Global Database
   2. Amazon DynamoDB global tables
   3. Amazon RDS for MySQL with Multi-AZ enabled
   4. Amazon RDS for MySQL with a cross-Region snapshot copy
2. A financial services company requires a globally distributed database with zero data loss (RPO = 0) and strong consistency across all regions. Which solution should they choose?
   1. Amazon Aurora Global Database
   2. Amazon DynamoDB Global Tables with MREC
   3. Amazon DynamoDB Global Tables with MRSC
   4. Amazon RDS with cross-region read replicas
3. A company needs a multi-region database that supports writes in all regions simultaneously with automatic failover. Which solution provides this capability?
   1. Amazon Aurora Global Database
   2. Amazon DynamoDB Global Tables
   3. Amazon RDS Multi-AZ
   4. Amazon Aurora with read replicas
4. What is the primary difference between Aurora Global Database and DynamoDB Global Tables in terms of write operations?
   1. Aurora supports writes in all regions, DynamoDB only in primary region
   2. Aurora supports writes only in primary region, DynamoDB supports writes in all regions
   3. Both support writes in all regions
   4. Both support writes only in primary region
5. A company needs to deploy a DynamoDB Global Table with MRSC. How many regions must they deploy in?
   1. Minimum 2 regions
   2. Exactly 3 regions
   3. Up to 5 regions
   4. Unlimited regions
6. Which of the following statements about Aurora Global Database and DynamoDB Global Tables are correct? (Select TWO)
   1. Aurora Global Database requires manual failover, DynamoDB Global Tables support automatic failover
   2. Aurora Global Database supports NoSQL, DynamoDB supports SQL
   3. DynamoDB Global Tables offer 99.999% availability, Aurora offers 99.99%
   4. Aurora Global Database supports multi-active writes
   5. DynamoDB MRSC has higher replication latency than Aurora

References

• AWS Aurora Global Database
• AWS DynamoDB Global Tables
• Multi-Region strong consistency for DynamoDB
• Build the highest resilience apps with multi-Region strong consistency