Ruby on Rails Code Review Checklist

Ruby on Rails (RoR) remains one of the most popular frameworks for rapid web development, but apps built with RoR require careful reviews to maintain reliability as they grow. At Redwerk, we’ve built, audited, and optimized Rails apps for over a decade. This Ruby on Rails code review checklist encapsulates our proven approach to preventing performance bottlenecks, patching security gaps, and ensuring a clean, maintainable codebase.

Preliminary Checks

Before inspecting a single method or model, set the stage for a productive review. Preliminary checks clarify objectives and streamline collaboration from the start. Skipping these checks can lead to missed context, overlooked dependencies, and an inefficient review process.

Gather Requirements & Architecture:

Review project documentation: features, architecture diagrams, and deployment strategies
Identify any critical modules (e.g., payment processing, real-time features) that demand extra scrutiny

Collect Codebase & Docs:

Ensure you have the latest code from version control (Git, GitHub, or GitLab)
Gather relevant documentation: API specs, DB schemas, and config files
Look at issue trackers to spot recurring bugs or feature requests

Define Review Goals:

Choose focus areas: security, scalability, maintainability, or all of the above
Outline success criteria: fewer vulnerabilities, better response times, etc.

Environment Setup:

Mirror production configurations for accurate testing
Confirm you have access to the necessary databases and external services
Use the same Ruby and Rails versions as production

Tool Selection:

Code Quality: RuboCop for style checks
Security: Brakeman for static analysis
CI Integration: Automate checks on each commit or pull request

Code Quality & Maintainability

Readable, well-structured code scales faster and handles updates without causing drama. It also reduces onboarding time for new developers, ensuring a steady knowledge transfer within the team. By establishing consistent coding standards, you create a solid foundation that can adapt as project requirements evolve.

Follow Rails & Ruby Style:

Align with established style guides (e.g., Ruby Style Guide)
Keep naming consistent: singular model names, snake_case for methods

Keep Methods & Classes Tidy:

Adhere to the single responsibility principle—avoid mega-controllers or bloated services
Split large classes into modules or service objects where logical

Avoid Duplication:

Factor out repeated logic into helpers, concerns, or shared service objects
Use DRY code to reduce maintenance headaches and bugs

Error Handling:

Rescue exceptions consistently, providing user-friendly messages
Don’t expose sensitive system details in logs or error pages

Documentation & Comments:

Document public methods with brief RDoc or YARD comments
Remove outdated comments that no longer reflect the code

Testing & Coverage:

Ensure RSpec or MiniTest covers critical paths
Check coverage for edge cases, not just the “happy path”

Syntax & Language Constructs

Ruby offers expressive features that can shorten code, but be cautious of hidden traps. Overusing certain shortcuts or metaprogramming techniques can lead to unreadable and error-prone code. Consistent syntax helps your team quickly understand and maintain even the most complex logic.

Leverage Ruby Idioms:

Use symbols for hash keys ({ user_id: 42 }), and avoid unnecessary string literals
Stick to do…end vs. {} consistently for blocks

Control Flow & Methods:

Use guard clauses (return unless current_user) instead of nested ifs
Keep methods small and self-explanatory

Blocks & Iterators:

Favor higher-order enumerators (map, select) for clarity
Avoid triple-nested loops; break large tasks into smaller methods

Rails Conventions:

Pay attention to the MVC pattern: keep business logic out of controllers
Use ActiveModel validations for data integrity

Exception Usage:

Raise exceptions only for truly exceptional cases
Provide meaningful error messages to simplify debugging

Security Best Practices

RoR offers solid security defaults, but oversight can undermine them. Overlooked vulnerabilities can escalate into serious breaches, jeopardizing user trust and regulatory compliance. By following a structured approach, like the one outlined in our security code review checklist, you can systematically identify and mitigate potential weaknesses early on.

Strong Parameters:

Whitelist fields in controllers to block malicious input
Rely on mass assignment protections to guard sensitive attributes

SQL Injection Prevention:

Use Rails query methods (find_by, where) with symbol keys
Avoid raw SQL; if you must, sanitize inputs carefully

XSS & CSRF Defenses:

Don’t bypass Rails’ escaping with raw or html_safe unnecessarily
Keep protect_from_forgery active in controllers

Authentication & Authorization:

Use libraries like Devise, CanCanCan, or Pundit for authorization
Validate user roles before accessing restricted resources

Data Protection:

Don’t store passwords or keys in the repo—use Rails-encrypted credentials
Comply with relevant privacy laws (e.g., GDPR)

Regular Security Audits:

Automate scans with Brakeman
Keep an eye on gem updates—patch vulnerabilities promptly

Performance Optimization

A sluggish Rails app will inevitably lose users. Keeping response times low demands efficient data handling, caching, and background processing. For instance, while building a large-scale cleaning marketplace for CleanAgents, we optimized queries, added targeted caching, and implemented background jobs to handle intensive operations. Below are some of the best practices we find essential.

ActiveRecord Efficiency:

Use select to limit columns instead of SELECT *
Avoid N+1 queries with includes or eager_load

Caching:

Implement fragment caching, Russian doll caching, or low-level caching
Explore Redis or Memcached to store frequently accessed data

Background Jobs:

Offload long-running tasks to Sidekiq, Resque, or Delayed Job
Track queue processing time to spot bottlenecks

Optimizing Views:

Move heavy computations out of templates
Serve assets via a CDN for faster load times

Profiling & Monitoring:

Use New Relic, Skylight, or Scout to identify performance bottlenecks
Regularly profile SQL queries with EXPLAIN

Database Interaction

Fine-tuning your database logic is crucial in Ruby on Rails. Suboptimal queries and neglected schema considerations can lead to performance bottlenecks, data inconsistencies, or security loopholes. Below are several key practices that will help keep your application’s database interactions efficient and reliable.

Query Construction:

Stick to where, find_by, pluck for data retrieval
Keep custom SQL limited to specialized cases and test them thoroughly

Transactions:

Group-related DB operations in transactions for atomic changes
Roll back on exceptions to preserve data integrity

Indexing & Constraints:

Add indexes to columns used in WHERE clauses or JOINS
Enforce foreign key constraints to maintain referential integrity

Batch Operations:

Use find_each or in_batches for large datasets to avoid memory bloat
Leverage background jobs for chunk processing if needed

Migrations:

Write reversible migrations
Confirm migrations in a staging environment before production

Version Control & Collaboration

Solid Git workflows will keep your Rails projects stable, and your team in sync. By clearly defining branching strategies and commit practices, you minimize merge conflicts and ensure traceability. Encouraging prompt, constructive code reviews fosters a culture of quality and speeds up overall development cycles.

Branching Strategy:

Use a consistent approach (Git Flow, GitHub Flow, trunk-based)
Merge often to avoid massive, conflict-heavy branches

Commit Discipline:

Keep commits small and topic-focused
Write clear messages detailing the “what” and “why”

Pull Requests & Code Reviews:

Provide thorough descriptions and link relevant tickets
Discuss potential side effects or database migrations

CI/CD Integration:

Automate RuboCop, RSpec, and Brakeman checks per PR
Keep main branches deployable at all times

Release & Tagging:

Tag stable releases (e.g., v2.1.0)
Maintain a concise changelog for each release version

Compliance

Legal and organizational requirements must never be overlooked. Non-compliance can lead to heavy fines, reputational damage, or even service shutdowns. By integrating compliance checks into your development pipeline, you ensure long-term stability that protects both your business and your users.

Regulatory Standards:

If handling personal data, verify GDPR and/or CCPA compliance
For healthcare or finance, consider HIPAA or PCI-DSS guidelines

Security Updates:

Stay on top of Rails security patches
Track gem versions to avoid known vulnerabilities

Data Privacy & Auditing:

Encrypt sensitive data at rest and in transit
Log relevant user actions to detect unauthorized access

Open-Source Licenses:

Review licenses for third-party gems
Comply with usage terms to avoid legal complications

The Bottom Line

A robust Rails code review checks more than just syntax; it ensures your application is secure, performant, and future-proof. By systematically following each step—preliminary setup, syntax audits, security checks, performance tuning, and compliance—you’ll ship code that’s both easy to scale and safe to deploy.

At Redwerk, we provide quality RoR development services, helping businesses across North America and Europe create new revenue streams with robust marketplaces. We’ve audited Ruby on Rails solutions for government agencies, green tech startups, online marketplaces, and digital media platforms—pinpointing hidden code smells and security risks early on.

Do you have questions or need more hands-on support? Contact us at Redwerk. We’ll work together to help your RoR project reach its full potential.