Amazon DynamoDB global tables zero RPO?

Yes, DynamoDB zero-RPO ensures data is consistent across regions to ensure you have the latest committed data in all regions in the event of an issue in any single region. You pay a very slight latency penalty for write to avail of this feature.

It's definitely a challenge. In the past, solving for zero RPO involved synchronous replication across high-rtt links. But today, with this new DynamoDB feature, zero RPO involves synchronous replication across high-rtt links - in a distributed log - that then has to be materialized across silly numbers of replicas. You're not reading that wrong. Expect high write latency. You can still make efficient regional EC reads, but if you want consistent reads your read latencies will suffer - especially at the tail.

A final thought: how will you ensure that updates are idempotent?

Yes, you can indeed build applications with zero Recovery Point Objective (RPO) using Amazon DynamoDB global tables. This is a significant advancement in database technology, especially for multi-Region workloads.

DynamoDB global tables now offer a preview of multi-Region strong consistency, which allows you to build highly available multi-Region applications with an RPO of zero. This means your applications can always read the latest version of data from any Region in a global table, ensuring the highest level of resilience.

The multi-Region strong consistency feature ensures that your application is always reading the latest data, regardless of which Region it's accessing. This is particularly useful for applications with strict consistency requirements, such as user profile management, inventory tracking, and financial transaction processing.

It's important to note that this feature is currently in preview and available in select AWS Regions: US East (N. Virginia), US East (Ohio), and US West (Oregon). While it offers significant benefits, there are some limitations and considerations to keep in mind during the preview phase.

Using global tables with multi-Region strong consistency does come with some trade-offs. It requires exactly three replica tables and has specific quotas for write and read throughput. Additionally, it may have higher write and read latencies compared to the default eventual consistency model.

Despite these considerations, the ability to achieve zero RPO in a globally distributed database is a powerful capability that can significantly enhance the resilience and reliability of your applications, especially those serving users across multiple geographic regions.
Sources
Replicate DynamoDB Across Regions - Amazon DynamoDB Global Tables - AWS
Global tables with multi-Region strong consistency – preview - Amazon DynamoDB
Amazon DynamoDB global tables previews multi-Region strong consistency - AWS