@@ -43,6 +43,10 @@ Is it ok if all GitLab nodes have been updated, but the post-deployment migratio
Is it ok if all nodes have been updated, and then the post-deployment migrations get executed a couple days later, and then the background migrations take a week to finish?
### When upgrading a dependency like Rails
Is it ok that some nodes have the new Rails version, but some nodes have the old Rails version?
## A walkthrough of an update
Backwards compatibility problems during updates are often very subtle. This is why it is worth familiarizing yourself with [update instructions](../update/index.md), [reference architectures](../administration/reference_architectures/index.md), and [GitLab.com's architecture](https://about.gitlab.com/handbook/engineering/infrastructure/production/architecture/). But to illustrate how these problems arise, take a look at this example of a simple update.
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@@ -102,6 +106,13 @@ Yes! We have specific instructions for [zero-downtime updates](../update/index.m
## I've identified a potential backwards compatibility problem, what can I do about it?
### Coordinate
For major or minor version updates of Rails or Puma:
- Engage the Quality team to thoroughly test the MR.
- Notify the `@gitlab-org/release/managers` on the MR prior to merging.
### Feature flags
One way to handle this is to use a feature flag that is disabled by
