Gemfile of dreams: the libraries we use to build Rails apps

Cover for Gemfile of dreams: the libraries we use to build Rails apps


If you’re interested in translating or adapting this post, please contact us first.

From time immemorial, the Evil Martians team has worked on dozens of Ruby on Rails projects every year. Naturally, this process involves a lot of Ruby gems. Some reflect our desire to be cutting-edge and to use modern tools (or build our own!) Other gems are so flexible they’ve been used in most of our projects. Our development philosophies, programming habits, and soul are within this universe of Martian gems. So what would it look like if they were somehow able to converge into one gemfile—the ideal Martian Gemfile, the toolbox of the extraterrestrial Rails engineer?

Notice: This article is regularly updated to reflect the changes in the framework (Rails) and its ecosystem; for details, take a look at the Changelog.

The Rails ecosystem is quite vast. For (pretty much) every typical task, there are a number of libraries waiting to help you. How can we pick the right one for the job? We could rely on some specific metrics, like GitHub stars or the number of downloads (see The Ruby Toolbox for valuable insights). Or, we could draw from past experience: this approach works well but could lead to extreme conservatism.

Schedule call

Hire us to bring you superior productivity with Rails

Schedule call

At Evil Martians, we bet on our collective experience and alien instinct when choosing a gem or deciding to build a new one. The benefit of this collective experience is that it spans dozens of minds and years: we know which wins to repeat and which fails to avoid. While we cannot turn this knowledge into a super-smart chatty AI (yet), we can share a glimpse of it in this post.

The rest of the article is structured to resemble a Rails application Gemfile, and it contains the following sections:

Rails fundamentals

To begin, we need to configure the fundamental elements of a Rails web application: a web server and a database.
For our database, we’ll bet on PostgreSQL, while Puma will be our web server of choice. So, the beginning of our Gemfile looks like this:

gem 'rails', '~> 7.2'
gem 'pg'
gem 'puma'

There’s not much to add here, so let’s move on to the third pillar of Ruby on Rails applications: the background jobs engine.

Background jobs

The vital characteristic of web application performance is throughput (how many requests we can handle in a given time). Due to Ruby (MRI) concurrency limitations, more precisely Global Virtual Machine Lock (GVL), the number of requests that can be served in parallel is capped. To increase the throughput, we try hard to minimize request time; the best way to achieve this is by offloading as much work as possible to background execution. That’s where a background jobs processing engine comes into play.

Rails provides an abstraction, Active Job, to define background jobs. But it’s up to users to choose a specific processor implementation. No surprises here—we use Sidekiq:

gem 'sidekiq'

There are plenty of Sidekiq add-ons (including official Pro and Enterprise versions) which give you better control over background job execution logic. Let me share two of the most frequently used within Martian projects:

gem 'sidekiq-grouping'
gem 'sidekiq-limit_fetch'

The sidekiq-grouping gem allows you to buffer enqueued jobs and process them in batches. This is helpful when the enqueue rate is high, but you don’t need jobs to be instantly processed. A typical use case is re-indexing models, or broadcasting live updates to models.

To keep hard-working (and RAM-bloating) jobs under control, we use sidekiq-limit_fetch. For example, to avoid generating more than a single large XSLX export at a time, we configure a limit for the queue:

# sidekiq.yml
  - default
  # ...
  - exports
  exports: 1

You could certainly go with Sidekiq Pro or Enterprise and get all the features provided by third-party solutions and improved stability out of the box—that would definitely make your gem list much thinner (and your wallet, too. But, well, it’s worth it).

However, Sidekiq still comes with a couple of trade-offs whether or not you pay. First, it requires you to have Redis, an additional infrastructure component to maintain (or pay for). Second, using Redis for job storage is prone to transactional integrity errors (we talk about this problem and the solution below, so continue reading). Thus, in recent years, a movement for transaction-aware and dependency-free background job engines has gained a lot of popularity. It’s now common to see the following gems in Gemfiles:

gem 'good_job'

# or
gem 'solid_queue'

GoodJob uses PostgreSQL as a backend and so it can be easily integrated into any application that is already using this database (that is, most applications we work with). It provides a decent set of features, good enough for typical Rails applications, and has been used in the wild for quite some time, enough to be considered seriously. Its spiritual successor, SolidQueue, a database-agnostic (still, SQL-dependent) solution, aims to become Rails’ default answer to background jobs starting from Rails 8; but we prefer to wait for it become nice and mature.

One additional benefit of using GoodJob or SolidQueue is built-in support for recurrent jobs (cron-like). For non-Enterpise Sidekiq, you must use some third-party tool for that. Here is what you can find in some of our Gemfiles:

gem 'schked'

For recurrent jobs, we use a lightweight solution called Schked. It’s a wrapper over the well-known rufus-scheduler with some useful additional features, such as testing support and Rails Engines awareness.

Let’s finish this section with something that goes a bit beyound Rails:

gem 'faktory_worker_ruby'

In multi-language projects, we use Faktory to enqueue and process jobs from different services. For example, an ML service written in Python can send analysis results to a Rails application, and vice versa: a Rails app can send analysis requests to a Python app.

Active Record extensions

As you can see from the section title, we do not “derail” from the Rails Way: we use Active Record to model business logic and communicate with a database.

Active Record is the most feature-rich Rails sub-framework, and its API is growing with every Rails release (we even got Common Table Expressions support in Rails 7.1!) However, there’s still room for even more features, so we’ll add a bunch of plugins to make that happen.

Since we specialize in PostgreSQL, we use its specific features heavily. My personal favorite is JSONB. When used reasonably, it can give you a huge productivity boost (no need to worry about schema, migrations, and so on.) By default, Rails converts JSONB values to plain Ruby hashes, which are not so powerful in terms of modeling business logic. That’s why we usually back our unstructured fields using one of the following libraries:

gem 'store_attribute'
gem 'store_model'

The store_attribute gem extends the built-in Active Record store_accessor feature and adds type-casting support. Accordingly, your JSONB values can be treated as regular attributes.

Store Model goes further and allows you to define model classes backed by JSON attributes.

The other database features (not PostgreSQL, but SQL specific) from our Top-N list are views, triggers, and full-text search. Here are the corresponding gems:

gem 'pg_search'
gem 'postgresql_cursor'

gem 'fx'
gem 'scenic'
# or
gem 'pg_trunk'

Speaking of feature-like extensions, I’d like to mention just a couple of them:

# Soft-deletion
gem 'discard'
# Helpers to group by time periods
gem 'groupdate'

Discard provides a minimalistic soft-deletion functionality (with no default_scope attached). Being minimalistic makes it easy to customize to your needs, that’s why this gem is present in most applications where we softly delete data.

Groupdate is a must-have if you deal with time-aggregated reporting (and still haven’t migrated to a time-series database, like, say, TimescaleDB).

Authentication and authorization

Most of the applications I’ve worked on in the past five years have had this line in their Gemfile:

gem 'devise'

And I’d bet that nine out of ten readers have Devise in their bundles, too; this is just the current reality. (But, nevertheless, I want to dream.) In a less common situation, when building a Rails application from scratch, we always consider alternative authentication libraries first. And the leader is… drumroll… Rails itself! You can go pretty far with the has_secure_password feature. Rails 8 is planned to ship with a fancy generator to make it even easier to do that!

And there are a couple more candidates before giving up and falling back to Devise:

gem 'sorcery'
gem 'jwt_sessions'

Sorcery has been around for years. It’s less magical (despite stating the opposite in its README) and opinionated than Devise, and has a pluggable architecture (so you can easily pick the parts you need).

The JWT Sessions library provides everything you need to build token-based authentication. It’s perfect for building API-only Rails apps with mobile or SPA frontends.

Let’s skip the whole category of OAuth-driven authentication solutions (this question deserves its own post) and switch to authorization.

Wait, what? Isn’t that the same thing? Not at all. The fundamental difference comes down to the questions we’re answering. Authentication answers “Who’s there?”, while authorization answers “Am I allowed to do that?“. Thus, authorization deals with roles and permissions.

Authorization itself could be split into two components: an authorization model and authorization (enforcement) layer. The former represents the business logic behind permissions (whether you use roles, granular permissions, or whatever). The latter one, the authorization layer, defines how to apply the authorization rules.

An authorization model is too application-specific, while for implementing an authorization layer, we can use generic techniques (wrapped into gems). Historically, we’ve used Pundit to implement authorization enforcement, but today we have a better option:

gem 'action_policy'

Action Policy is Pundit on steroids. It uses the same concepts (policies) but provides more out-of-the-box features (performance and is developer-experience oriented.)

HTML views

The classic Rails Way assumes an HTML-first approach. A server is responsible for each part of the Model-View-Controller paradigm: that is, the “M”, the “V”, and the “C”. After the dark ages of API-only Rails apps, we’ve recently witnessed a renaissance of the HTML-over-the-wire approach in the Rails community. So, here we are, crafting view templates again!

However, in the 2020s, the way to do that is different as the toolbox:

gem 'view_component'
gem 'view_component-contrib'
gem 'lookbook', require: false

gem 'turbo-rails'

Hotwire makes our HTML-based applications interactive and reactive, while view components help us organize the templates and their logic.

Asset management

Dealing with assets in Rails has become tricky since the introduction of Webpacker in Rails 5. Today, in Rails 7, we have multiple official solutions to the problem (Import Maps, JS/CSS bundling gems). On Mars, however, we go another way:

gem 'vite_rails'

Using Vite is a middle ground between backend-oriented and frontend-oriented assets management. It’s simple to use for both Hotwire applications and React SPAs (and we often have hybrid setups). Further, the vite_ruby gem provides a five-star developer experience.

And here are a couple more assets-related goodies to add to our file:

gem 'imgproxy-rails'
gem 'premailer-rails'

Do you have to deal with a lot of user-generated content? Don’t waste your Ruby server resources for image transformations—let a dedicated proxy server do the hard work. Obviously, we use our own imgproxy, and with the companion gem, using it in Rails apps is a piece of cake.

When it comes to styling emails, the premailer-rails gem is truly a gem of a gem. Use your CSS classes freely and let Premailer unwrap them into style attributes during email template rendering.

Crafting APIs (and GraphQL)

Even though the HTML-over-the-wire approach is gaining back its popularity, years of JS domination won’t be so easily undone. And so, API-first Rails applications don’t seem like they’re going anywhere.

When crafting JSON APIs, we usually use the following tools:

gem 'alba'
gem 'oj'
# or
gem 'panko_serializer'

Both Alba and Panko focus on data serialization performance and provide familiar (Active Model Serializer-like) interfaces. Panko is the fastest serialization library (due to its use of a C extension) amongst the currently maintained and closer resembles active_model_serializers API (so it’s a good candidate for migration). On the other hand, Alba is more feature-rich and pretty fast, too (when using Oj as a JSON serialization driver).

Dealing with REST API documentation and its syncrhonization with frontend counterparts is yet another common challenge for Rails developers. We’ve found that a documentation-first approach works pretty good: craft your OpenAPI schema by hand or with AI help (it’s 2024 🤖) and make sure your implementation agrees with the schema:

gem "skooma", group: :test

No additional flourishes are needed to keep documentation and types in sync is required if you use GraphQL (which is still quite popular in the Rails community):

gem 'graphql', '~> 2.3'

# Cursor-based pagination for connections
gem 'graphql-connections'
# Caching for GraphQL done right
gem 'graphql-fragment_cache'
# Support for Apollo persisted queries
gem 'graphql-persisted_queries'

# Yes, Action Policy comes with the official GraphQL integration!
gem 'action_policy-graphql'

gem 'graphql-schema_comparator', group: :development

# Solving N+1 queries problem like a (lazy) pro!
gem 'ar_lazy_preload'

Most of the GraphQL libraries we use are performance-oriented (and Martian built …coincidence?) The graphql-schema_comparator gem is used along with Danger to warn pull request reviewers about schema modifications (so they can pay proper attention to the change.)

You may ask why we added the ar_lazy_preload gem to the GraphQL group. Despite being an Active Record extension, this library is especially handy in conjunction with GraphQL APIs, where classic N+1 busters like #preload and #eager_load are not so efficient. With lazy preload, we can avoid both performance regressions and any complexity overhead from using data loaders or batch loaders (although not completely, of course).

Logging and instrumentation

The production group of our mythical Gemfile contains logging and monitoring tools:

group :production do
  gem 'yabeda-sidekiq', require: false
  gem 'yabeda-puma-plugin', require: false

  gem 'lograge'

Yabeda is an instrumentation framework for Ruby and Rails apps. It comes with plugins for popular libraries (like Sidekiq and Puma) and monitoring backends (Prometheus, DataDog, etc.).

Lograge turns verbose Rails output into concise structured logs, which can be parsed by log collection systems and turned into queryable data sources.

In the default group, we also have this (anti-)logging gem:

gem 'silencer', require: ['silencer/rails/logger']

Since Rails’ addition of the default health-checking endpoint, our logs became full of useless GET /up lines. To shut them up, we add the silencer gem and configure it as follows:

# config/initializers/silencer.rb
Rails.application.configure do
    silence: ["/up"]

Development tools

Let’s move from production to development—our actual work as engineers. Ruby is designed for developer happiness, but to make developing applications with Ruby follow through with this principle, we need to tweak our dev tools a bit. What makes a Rails developer really happy? Having zero trouble with the development environment 🙂 Docker solves this problem well enough. What else? Doing less boring work. So, we’ll add robots to help us with that so we can focus on cool things. Or, we add gems to make our developer experience more pleasant and help us write better code.

Below we list popular development tools used by Martians in Rails projects.

gem 'bootsnap', require: false

Bootsnap is a part of the Rails default bundle, so no introduction is required. Just use it!

gem 'database_validations'
gem 'database_consistency'

This pair of gems, database_validations and database_consistency, helps you to enforce the consistency between your model layer and the database schema. If it’s null: false, then it must have validates :foo, presence: true. If it validates :bar, uniqueness: true then a unique index should be defined for the column(-s).

gem 'isolator'
gem 'after_commit_everywhere'

Since we usually run on a transactional database, we should always remember about ACID. Database transactions are not the same as logical transactions, non-database side-effects are not protected by the database, and we should take care of them ourselves. For example, sending a “Post published” email from within a database transaction could result in a false positive notification in case the transaction would fail to commit. Similarly, performing an API request could lead to inconsistency in the third-party system (e.g., a payment gateway) in case of a rollbacked transaction. Isolator helps to identify such problems and after_commit_everywhere provides a convenient API to perform side-effects on successful COMMIT. Rails 7.2 comes with a similar feature, ActiveRecord::Transaction#after_commit, as well as an option to automatically enqueue Active Job jobs on commit, so you might not need the after_commit_everywhere gem anymore.

More database-related goodies with short annotations:

# Make sure your migrations do not cause downtimes
gem 'strong_migrations'
# Get useful insights on your database health
gem 'rails-pg-extras'

# Create partial anonymized dump of your production database to perform
# profiling and benchmarking locally
gem 'evil-seed'

Benchmarking and profiling is a part of the development process; here are some of the gems to help with it:

# Speaking of profiling, here are some must-have tools
gem 'derailed_benchmarks'
gem 'rack-mini-profiler'
gem 'stackprof'
gem 'vernier'

Speaking of Stackprof, we can’t help but mention an awesome stack profiling reports viewer—Speedscope. For projects running on Ruby 3.2+, we recommend using Vernier, a next-gen Ruby sampling profiler with built-in support for Rails instrumentation events and more.

gem 'bundler-audit', require: false
gem 'brakeman', require: false

Security is a must. Check for any known CVEs in your dependencies by running bundle audit and scan your codebase for security breaches regularly with Brakeman. Nowadays, CI services provide their own security analysis tools which can be used instead.

gem 'danger', require: false

Danger can level up your code review experience by automating routine tasks and highlighting important changes: automatically attach labels, warn about missing tests or undesired structure.sql changes—delegate pretty much whatever you want to automation scripts.

gem 'next_rails'

Upgrading Rails? The next_rails gem can guide you through the process.

gem 'attractor'
gem 'coverband'

Keeping codebases in a healthy state requires us to perform regular check-ups and monitor the parts of your code that are hurting the most. You can use static analysis, for example, the famous churn/complexity technique to identify the components worth refactoring. There are plenty of tools for that, but our choice is Attractor. Production coverage (via Coverband) provides a different perspective on which code is more important (and thus requires more attention during refactoring); it also identifies any dead code to be eliminated.

Here’s the final chord in this little symphony:

eval_gemfile 'gemfiles/rubocop.gemfile'

# gemfiles/rubocop.gemfile
gem 'standard'
gem 'rubocop-rspec'
gem 'rubocop-rails'

You can learn more about our RuboCop-ing approach in the corresponding post: RuboCoping with legacy: Bring your Ruby code up to Standard.

Testing tools

Writing and running tests is also a part of everyday development, but it should still be treated with a personal touch. A highly advanced testing culture is one of the most significant benefits of building applications with Ruby and Rails.

Let’s start with the basics:

gem 'rspec-rails'
gem 'factory_bot'

Yes, we are RSpec fans, and we prefer factories (via FactoryBot ) over fixtures (but not exclusively). Let’s leave a heated discussion on Minitest vs. RSpec and Factories vs. fixtures for another day and continue with paradigm-agnostic libraries.

gem 'cuprite'
gem 'site_prism'

gem 'capybara-thruster'

Crafting fast and robust system tests (or browser tests) is a combination of modern tooling to control the browser (Cuprite) and an object-oriented approach to describing scenarios (via site_prism’s page objects).

Capybara Thruster is a micro-gem which allows you to use Thruster as a web server for system tests. While we haven’t fully embraced Thruster as a production server (or even as a development application server), we’ve found it really useful for browser-based testing. This is mostly due to its ability to serve assets blazingly fast, thus decreasing page load times. For projects using AnyCable, it’s a must have since you can run AnyCable server without any additional hacks via our special AnyCable Thruster distribution.

gem 'with_model'

The with_model gem is one of our favorites. I first discovered it many years ago when I was looking for a better way to test Rails model concerns. The library allows you to create temporary models backed by temporary database tables to test modules, Rails concerns, and any code implementing a shared behavior.

gem 'n_plus_one_control'

The N+1 queries problem is one of the most frequent issues with Rails applications: it’s so easy to introduce it, and there are some tools to detect it, but not to prevent it (except the recent .strict_loading Active Record feature). With n_plus_one_control gem, you can write tests to protect yourself from introducing N+1 queries in the future.

gem 'webmock'
gem 'vcr'

Tests should never access the outer world. My rule of thumb is as simple as this: a test suite is only good if I can run it while being on a plane and it passes. Simply dropping WebMock.disable_net_connect! to a rails_helper.rb or test_helper.rb can help you to avoid dependency on real network calls.

Network calls (and time, too) could also cause your tests to have flakiness:

gem 'zonebie'

One elegant way to prevent time-dependent tests is to run them in a random time zone. The zonebie gem does this by just being included in the bundle.

Note that we haven’t included the famous Timecop gem to control time: that’s because it’s redundant for Rails apps. Instead, you can use built-in time helpers.

gem 'rspec-instafail', require: false
gem 'fuubar', require: false

A couple of goodies for RSpec users: Fuubar is a progress bar formatter (why isn’t it the default?), and the rspec-instafail formatter is useful when running tests on CI (so you can see any errors right away and start fixing them before the entire test suite has finished).

And last, but not least, our final ingredient to our Gemfile’s test group:

gem 'test-prof'

TestProf is a “good doctor for slow Rails test suites”. It doesn’t matter if you have hundreds or dozens of thousands of tests, it’s always worth it to make them run faster. And with TestProf, you can drastically improve test run time with little effort.

Everything else

It’s basically impossible to describe all the awesome libraries we use in just a single blog post; so we picked a handful of bonus libraries to share here:

gem 'anycable-rails'

gem 'feature_toggles'

gem 'redlock'

gem 'anyway_config'

gem 'retriable'

gem 'nanoid'

gem 'dry-initializer'
gem 'dry-monads'
gem 'dry-effects'

Each one of the above answers a particular question:

  • Want to build some real-time features? AnyCable is the key.
  • Need to quickly introduce feature toggling? There is a minimalistic solution for that: feature_toggles.
  • Looking for a distributed locking mechanism? Redis works great for that, and redlock is the way to go.
  • Want to keep application configuration under control? Consider using configuration classes via Anyway Config.
  • Tired of writing retry logic by hand? Take a look at retriable.
  • Need a fast and controllable way of generating unique identifiers? Check out nanoid (a port of Martian Andrey Sitnik’s nanoid JS).
  • Service objects a mess? Consider standardizing them with a sprinkle of dry-rb. For instance, declarative parameters from dry-initializer and/or Result objects from dry-monads (they work especially well with pattern matching).
  • Want to move the context around abstraction layers in a safer and predictable way? Try algebraic effects via the dry-effects library.

I could go on and on with questions and answers like this, but I don’t want to be too pushy. Every engineer has their own ideal tool belt; try and build your own! Use other kits as a reference—not a source of truth.

Only in dreams

On that note, this is a good place to snap back to reality. Hopefully, you have some conception of what the “ideal” Martian Gemfile might look like, and with any luck, you’ve got some inspiration to dream a little on your own, too. And if you’re looking for a good bedtime book to make sure your dreams are gem-filled and glorious, consider “Layered Design for Ruby on Rails applications”, by yours truly (and don’t be surprised when you see most of the gems from this post within its pages).

P.S. Sometimes dreams turn into nightmares

Evil Martians can help with your project and product design needs. So whether it’s the Rails project of your dreams (or something beyond) if you have a web or mobile application in need of expert problem solving with product design, frontend, backend, or software reliability, we’re ready! Or are you looking to get your project off the ground and into reality? Reach out to us!


1.1.0 (2024-05-30)

  • Mention

  • Mention “Layered design for Rails”.

  • Add nanoid.

  • Add capybara-thruster.

  • Add vernier.

  • Add silencer with an example.

  • Add skooma.

  • Add imgproxy-rails.

  • Remove activerecord_postgres-enum (Rails now supports enums).

  • Added good_job and solid_queue.

1.0.1 (2023-01-20)

  • Replace redis-mutex with redlock (because even the author suggests this)

Hire us to bring you superior productivity with Rails

You will feel improvement in velocity and developer happiness in as little as one week with our expert work in bringing best tools for your needs, and upskilling the team.

Book a call
Launch with Martians

Let's solve your hard problems

Martians at a glance
years in business

We're experts at helping developer products grow, with a proven track record in UI design, product iterations, cost-effective scaling, and much more. We'll lay out a strategy before our engineers and designers leap into action.

If you prefer email, write to us at