Preparation checklist for global tables - AWS Prescriptive Guidance

Preparation checklist for global tables

Use the following checklist for decisions and tasks when you deploy global tables.

  • Determine how many and which Regions should participate in the global table.

  • Determine your application’s write mode.

  • Plan your routing strategy, based on your write mode.

  • Define your evacuation plan, based on your write mode and routing strategy.

  • Capture metrics on the health, latency, and errors across each Region. For a list of DynamoDB metrics, see the AWS blog post Monitoring Amazon DynamoDB for operational awareness. You should also use synthetic canaries (artificial requests designed to detect failures) as well as live observation of customer traffic. Not all issues appear in the DynamoDB metrics.

  • Set alarms for any sustained increase in ReplicationLatency. An increase might indicate an accidental misconfiguration in which the global table has different write settings in different Regions, which leads to failed replicated requests and increased latencies. It could also indicate that there is a Regional disruption. A good example is to generate an alert if the recent average exceeds 180,000 milliseconds. You might also watch for ReplicationLatency dropping to 0, which indicates stalled replication.

  • Assign sufficient maximum read and write settings for each global table.

  • Identify the conditions where you would evacuate a Region. If the decision involves human judgment, document all considerations. This work should be done carefully in advance, not under stress.

  • Maintain a runbook for every action that must take place when you evacuate a Region. Usually very little work is involved for the global tables, but moving the rest of the stack might be complex.

    Note

    With failover procedures, it’s best practice to rely only on data plane operations and not on control plane operations, because some control plane operations might be degraded during Region failures. For more information, see the AWS blog post Build resilient applications with Amazon DynamoDB global tables: Part 4.

  • Test all aspects of the runbook periodically, including Region evacuations. An untested runbook is an unreliable runbook.

  • Consider using AWS Resilience Hub to evaluate the resilience of your entire application (including global tables). This service provides a comprehensive view of the resiliency status of your application portfolio through its dashboard.

  • Consider using Route 53 ARC readiness checks to evaluate the current configuration of your application and track any deviances from best practices.

  • When you write health checks for use with Route 53 or Global Accelerator, make a set of calls that cover the full database flow. If you limit your check to confirm only that the DynamoDB endpoint is up, you won’t be able to cover many failure modes such as AWS Identity and Access Management (IAM) configuration errors, code deployment problems, failure in the stack outside DynamoDB, higher than average read or write latencies, and so on.