The Case Against Monkey Patching

Monkey Patching: A Sustainable Alternative for Ruby on Rails

Monkey patching has been celebrated as one of Ruby’s most powerful features, allowing developers to quickly modify or extend behavior in frameworks and libraries. For many, it feels like a quick solution to immediate problems. But while monkey patching may solve issues in the short term, it often introduces significant long-term challenges.

At HeroDevs, we’ve worked with countless teams dealing with the consequences of relying too heavily on monkey patches. From broken dependencies to upgrade paralysis, the impact can be crippling.

What Is Monkey Patching? And Why Do Developers Use It?

Monkey patching, the practice of modifying classes and methods at runtime, has long been a controversial feature in dynamic programming languages, particularly in Ruby. While it offers quick solutions to immediate problems, its long-term impacts on codebases deserve careful scrutiny.

Monkey patching allows developers to modify or extend existing code at runtime, including core language features and third-party libraries. For example, a developer might add a new method to Ruby's String class:

(code 
class String
  def reverse_and_upcase
    self.reverse.upcase
  end
end)

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However, monkey patches operate globally. They don’t just affect the area you’re working on; they can have unintended consequences throughout the entire application. This makes them risky, unpredictable, and difficult to manage as your codebase evolves.

Maintenance Burden

Research from a 2023 analysis of 500 Ruby on Rails applications revealed:

• Projects with extensive monkey patching took 35% longer to upgrade between major versions
• Codebases with more than 10 monkey patches had 2.3x more production incidents
• Teams spent an average of 15-20 hours per monkey patch during major version upgrades

Security Implications

Security audits across enterprise Rails applications showed:

• 23% of monkey patches inadvertently bypassed security controls
• Applications with monkey-patched core methods experienced 40% more security vulnerabilities
• 15% of patches directly conflicted with security updates in newer versions

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Why Monkey Patching Creates Long-Term Challenges

Upgrading Rails is essential to accessing new features, improving performance, ensuring security, and resolving bugs. But monkey patches can make this process incredibly challenging—if not outright impossible.

Here’s why:

• Private APIs Are Fragile: Monkey patches often rely on internal or private APIs, which aren’t protected by deprecation warnings. When these APIs change or are removed in a new version of Rails, your patches will break silently, leaving your application in an unstable state.
• Critical Path Vulnerabilities: Patching methods or behaviors in critical paths of your application can block upgrades entirely. If the underlying functionality you’ve patched is restructured or deprecated in a newer version, you may find no viable way to move forward.
• Time-Consuming Fixes: Rewriting patches to work with new versions of Rails is tedious, time-consuming, and error-prone. What might seem like a minor fix can quickly balloon into weeks or months of effort.

Instead of gaining the benefits of an upgrade, your team ends up fighting fires—revisiting patches, rewriting dependencies, and debugging why things no longer work.

Security Risks Lurk Beneath the Surface

Monkey patches can also compromise your application’s security. A patch might unintentionally override upstream fixes, reintroducing vulnerabilities that would otherwise be resolved by upgrading.

For example, a security flaw discovered in Rails might be patched in a new version, but your monkey patch could bypass the fix altogether. Worse, many patches are undocumented or forgotten, leaving teams unaware of the risks they’ve created.

Security releases are designed to protect your application from known vulnerabilities. Monkey patches undermine this safety net, putting your business at risk.

Technical Debt Piles Up Quickly

Technical debt is inevitable in any software project, but monkey patching accelerates it dramatically. Patches are often introduced as “temporary” fixes but rarely come with proper documentation or testing. Over time, they become entrenched in your codebase, making it harder to understand how things work—or why certain behaviors exist.

This debt becomes especially painful during upgrades or production incidents. Teams are left untangling a web of undocumented changes, struggling to identify what’s causing an issue or how to fix it.

Unintended and Unpredictable Consequences

Monkey patches don’t operate in isolation. They affect every part of your codebase that interacts with the patched behavior, often in ways you didn’t anticipate.

For example, patching ActiveRecord might work well for your primary use case but introduce edge-case bugs in other parts of your application. Diagnosing these issues is a monumental challenge—especially when the original developer who implemented the patch is no longer available.

Why Monkey Patching Isn’t the Solution You Think It Is

Monkey patches are often a last resort, introduced when teams feel they have no other option. But this approach is unsustainable. Every patch you add increases complexity, risk, and technical debt, locking you into a cycle of firefighting.

At HeroDevs, we believe there’s a better way to address these challenges.

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How HeroDevs’ Never-Ending Support Solves This Problem

With Never-Ending Support (NES), we help teams avoid the pitfalls of monkey patching by providing long-term support and security updates for older versions of Ruby on Rails—2.3, 3.2, 4.2, 5.2, and 6.1.

Here’s how NES works:

• Tailored Security Updates: We deliver fixes to keep your Rails version protected against known vulnerabilities, eliminating the need for risky patches.
• Dependency Remediation: Our team addresses gem and library incompatibilities, ensuring your application runs smoothly without requiring invasive changes.
• Bug Fixes Without Upgrades: NES resolves critical issues in your framework so you can avoid disruptive migrations.

By partnering with HeroDevs, you can focus on building features and delivering value, knowing your application is secure and stable.

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A Smarter Approach to Managing Dependencies

Before reaching for a monkey patch, consider these alternatives:

1. Is an upgrade possible? In many cases, the issue you’re experiencing may already be resolved in a newer version of the library or framework.
2. Can HeroDevs handle it? With NES, we maintain your Rails version, providing the updates and fixes you need.
3. Is this patch absolutely necessary? Revisit the documentation or explore alternative solutions before introducing a change.

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Build a Future Without Monkey Patching

Monkey patching may have been a hallmark of Ruby’s flexibility, but it’s time to move beyond this unsustainable practice. With Never-Ending Support, you can keep your Rails applications secure, stable, and maintainable—without the headaches of quick fixes that break later.

Let’s work together to eliminate monkey patches and build a stronger foundation for your applications. Refer here to Learn More, or schedule a call with our sales team to see how we can help!

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