Upgrading a Ruby on Rails app can feel a bit like refactoring your workspace. You know it’s good for your application, but you’re not always sure where to start or what you might uncover along the way.
The truth is, every Rails upgrade comes with its own set of challenges. But with a little preparation, you can turn a potential issue into a smooth, structured process. Let’s look at some of the common challenges our teams at Railsfactory face and how we get ahead of them.
1. Gem Compatibility Issues
You know the feeling. You run bundle update and suddenly half your app starts throwing errors. Gem dependencies often break during upgrades because many libraries aren’t maintained in sync with Rails versions.
How to prepare:
Audit your gems early. Check for deprecated or unmaintained gems before starting the upgrade. (Tip: You can use Railsup , our free gem compatibility checker, to quickly see which gems need attention.)
2. Deprecated Features and Syntax Changes
Rails loves progress, which means older methods and syntax sometimes get left behind. You might find warnings piling up or tests failing unexpectedly.
How to prepare:
Review the Rails release notes for deprecations in advance. Catching these early saves time later when your app is already running on the newer version.
3. Test Coverage Gaps
An upgrade without proper test coverage is like flying blind. If tests are missing or flaky, it’s hard to know whether your app still behaves as expected post-upgrade.
How to prepare:
Before diving in, strengthen your test suite. Even basic coverage of critical features can prevent significant challenges in production.
4. Environment Differences
Sometimes, things run perfectly in development but break in staging or production. Different environment settings, gems, or data loads can cause inconsistencies.
How to prepare:
Simulate production locally or use a staging setup that mirrors it closely. Validate migrations, caching, and configuration changes before deploying.
5. Performance Regressions
Upgrades can introduce subtle performance drops especially when newer frameworks handle caching or queries differently.
How to prepare:
Benchmark key workflows before and after the upgrade. This helps you spot regressions quickly and ensures performance stays consistent (or improves!).
6. Autoloading and Naming Mismatches
Rails’ autoloading mechanism (especially with Zeitwerk) enforces stricter naming conventions. A single mismatch between a file path and a class name can break the app in unexpected ways.
How to prepare:
Run bin/rails zeitwerk:check before upgrading. Fix inconsistent file naming or module nesting. This step sounds small but prevents a surprising amount of “constant not found” chaos once you upgrade.
7. Config Defaults That Shift Over Time
Rails often updates default configurations from time zone handling to ActiveStorage, mailer behavior, or even middleware order. These changes can silently alter your app’s behavior.
How to prepare:
After running rails app:update, review each generated config file and compare it to your existing setup. Merge intentionally rather than automatically. Being deliberate here prevents subtle issues from surfacing once you deploy.
8. Data Migration and Schema Drift
When your schema has evolved over years, even a minor Rails version bump can expose outdated migrations or type mismatches , especially around timestamps, enums, or foreign keys.
How to prepare:
Clone production data into a staging environment and run migrations there first. Look for warnings, conflicts, or long-running operations. Data issues are rarely visible in dev, but they can be showstoppers in production.
Wrapping Up
Rails upgrade is rarely a straightforward process, and that is okay. The key is to plan ahead, take small steps, and document as you go.
If you’re planning an upgrade soon, grab our Rails Pre-Upgrade Checklist , a free resource to help you evaluate your app’s readiness and map out each stage with confidence.
Because sometimes, the best way to tackle challenges is to prepare for them before they even show up.
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