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The future is bright Mar 30, 2025 On Amazon Prime Video’s move to a monolith May 14, 2023 One size does not fit all: neither cloud nor on-prem Apr 10, 2023 Some thoughts on the latest LastPass fiasco Mar 5, 2023 Comparing AWS SQS, SNS, and Kinesis: A Technical Breakdown for Enterprise Developers Feb 11, 2023 There is no such thing as one grand unified full-stack programming language May 27, 2022 Which AWS messaging and queuing service to use? Jan 25, 2019 Using Markov Chain Generator to create Donald Trump's state of union speech Jan 20, 2019 Adobe Creative Cloud is an example of iPad replacing a laptop Jan 3, 2019 Facebook is the new Microsoft Apr 14, 2018 Leaving Facebook and Twitter: here are the alternatives Mar 25, 2018 Rather than innovating Walmart bullies their tech vendors to leave AWS Jun 27, 2017 Architecting API ecosystems: my interview with Anthony Brovchenko of R. Culturi Jun 5, 2017 TDWI 2017, Chicago, IL: Architecting Modern Big Data API Ecosystems May 30, 2017 Online grocers have an additional burden to be reliable Jan 5, 2017 Windows 10: a confession from an iOS traitor Jan 4, 2017 What I learned from using Amazon Alexa for a month Sep 7, 2016 Why I switched to Android and Google Project Fi and why should you Aug 28, 2016 Amazon Alexa is eating the retailers alive Jun 22, 2016 In search for the mythical neutrality among top-tier public cloud providers Jun 18, 2016 What can we learn from the last week's salesforce.com outage ? May 15, 2016 Why it makes perfect sense for Dropbox to leave AWS May 7, 2016 Our civilization has a single point of failure Dec 16, 2015 IT departments must transform in the face of the cloud revolution Nov 9, 2015 Setting Up Cross-Region Replication of AWS RDS for PostgreSQL Sep 12, 2015 Top Ten Differences Between ActiveMQ and Amazon SQS Sep 5, 2015 What Every College Computer Science Freshman Should Know Aug 14, 2015 Ten Questions to Consider Before Choosing Cassandra Aug 8, 2015 Big Data Should Be Used To Make Ads More Relevant Jul 29, 2015 Book Review: "Shop Class As Soulcraft" By Matthew B. Crawford Jul 5, 2015 Attracting STEM Graduates to Traditional Enterprise IT Jul 4, 2015 Smart IT Departments Own Their Business API and Take Ownership of Data Governance May 13, 2015 Guaranteeing Delivery of Messages with AWS SQS May 9, 2015 We Need a Cloud Version of Cassandra May 7, 2015 The Clarkson School Class of 2015 Commencement speech May 5, 2015 Building a Supercomputer in AWS: Is it even worth it ? Apr 13, 2015 Ordered Sets and Logs in Cassandra vs SQL Apr 8, 2015 Microsoft and Apple Have Everything to Lose if Chromebooks Succeed Mar 31, 2015 Where AWS Elastic BeanStalk Could be Better Mar 3, 2015 Trying to Replace Cassandra with DynamoDB ? Not so fast Feb 2, 2015 Why I am Tempted to Replace Cassandra With DynamoDB Nov 13, 2014 Infrastructure in the cloud vs on-premise Aug 25, 2014 Cassandra: a key puzzle piece in a design for failure Aug 18, 2014 Cassandra: Lessons Learned Jun 6, 2014 Things I wish Apache Cassandra was better at Feb 12, 2014

Setting Up Cross-Region Replication of AWS RDS for PostgreSQL

September 12, 2015

As of today AWS RDS for PostgreSQL1 does not offer cross-region replication. Short of switching to one of the RDS offerings that do support it, there is a few options to consider.

1. Custom Configured EC2 Instances with Master-Slave Replication


[caption id="attachment_222" align="aligncenter" width="300"]Master/slave light rail Master/slave light rail[/caption]

This setup sacrifices the benefits of AWS RDS service in exchange for greater control over replication settings. In this setup, one region hosts a master PostgreSQL host, and another region hosts a slave which can also act as a read-replica2.

Advantages


Greater control over replication settings.

Disadvantages



  • Give up all the advantages of running in AWS RDS environment.

  • Writes can only be performed in the master region.


2. Software-defined Two-phase Commit


[caption id="attachment_264" align="aligncenter" width="300"]Commitment Photo credit: Ed Schipul Commitment
Photo credit: Ed Schipul[/caption]

In this setup there are two independent AWS RDS instances. The application, however, utilizes a two-phase commit protocol3 to guarantee that all writes make it into both databases in a transactional fashion.

Advantages



  • Simple configuration

  • Does not sacrifice any of the AWS RDS advantages


Disadvantages



  • Responsibility for ensuring that writes make it into all regions fall onto the application itself.

  • Increased application code complexity.

  • Write performance is sacrificed since all regional databases must participate synchronously.


3. Asynchronous Writers


[caption id="attachment_266" align="aligncenter" width="300"]Fanning Out Photo credit: Tim Haynes Fanning Out
Photo credit: Tim Haynes[/caption]

In this approach each region hosts an asynchronous writer that listens on an SQS queue4. All writes are published on the SNS topic that is configured with all regional writer queues as subscriptions5. When the application running in any of the regions wants to write into the database it publishes a message on this SNS topic which then fans it out to all of the regional SQS queues.

Advantages



  • Simple configuration

  • Does not sacrifice any of the AWS RDS advantages

  • Does not sacrifice write performance


Disadvantages



  • Subject to software bugs

  • Subject to SNS and SQS bugs and outages

  • No guarantee of consistency

  • Requires a mechanism for periodically reconciling differences between regions







  1. AWS RDS for PostgreSQL ↩

  2. Configuring Master/Slave Replication with PostgreSQL ↩

  3. Distributed Transactions and the Transaction Manager ↩

  4. Amazon Simple Queue Service Documentation ↩

  5. SQS Queues and SNS Notifications – Now Best Friends ↩


Last updated January 20, 2026. Return to home.