Every second counts. Industry professionals, not so familiar with technology-rich world turn to web applications to get their business ahead in the digital journey, processing a minuscule amount of response time can make the difference. As faster site speed can leads to happier users and helps to improve the bottom line of your business. When it comes to Rails server its a fair game to handle load balancing, manage your apps reverse proxy requests and to fend DoS attacks.

Set the pace for your app’s speed as well as scalability

Choosing a Rails server can help you set the right pace for your application’s speed as well as scalabilty. As hardware is getting more robust, whereas cloud computing platforms are aiming to replace dedicated servers. There are numbers of popular Rails servers, but here I am going to discuss about three most popular Rails server products that has got major updates in the past few months. Therefore, I am writing this article to compare Rack – web servers to see if there is an actual slight difference in the performance. Let’s have a look.

Why an app’s raw speed is important?

An application’s raw speed is actually a factor for the vast majority of the applications. In Ruby’s app servers, the execution time of your HTTP calls, database queries, app code, likely dwarfs the millisecond difference in response times. Puma, Unicorn and and Passenger are plenty fast for almost every Ruby app.

However, I am not pointing out at benchmarked performance metrics, specifically those, which hammer an app server with hundreds of concurrent requests without throttling (ie siege -b). Because, this far from a realistic request pattern for almost every web app.

Unicorn: #1 Rails Server

In 2009, when James Pozdena introduced Unicorn, surprisingly it maintained an average a second response, even at the time of inscribed by concurrent request. James noted down the response time grew by as much as only a second with an each concurrent request.

However, as per the Nate Miller Unicorn’s speed was coming at a certain cost. While testing Unicorn as a replacement for a Mongrel deployment was causing a high number of 502 Bad Gateway errors. Miller also noticed a similar drop in an average time on Unicorn. On the other hand, Unicorn’s standard deviation for gateways errors surprisingly increased and raised concerns where the speed gains could leave the door open to increased instability.


It is an HTTP server designed for Rack applications to serve fast clients on high-bandwidth connections, low-latency and leverage the benefits of features in Unix/Unix-like kernels. Whereas, slow clients should only be served by placing a reverse proxy capable. Both the response and request in between unicorn and slow clients.



Passenger: #2 Rails Server

As per the Rails Core Team’s vote it is most “preferred way to deploy your Rails applications. After its significant update, Rails server comes in two flavors: Enterprise and open source. You can integrate this module directly with Apache or NGINX, so you can upload and run your application code with ease.

The most favourable thing is its deployment error resistance, where users can shut down all application processes when they encounter a glitch in an application’s code or a configuration error. The Enterprise edition enables debugging and enhanced monitoring, so it becomes really easy to get the source of an error in real time. As per the Phusion’s website over 150,000 top-notch companies are running apps with Passenger.


A modern web server and application server for Ruby, Python and Node.js, optimized for performance, low memory usage and ease of use.



Puma: #3 Rails Server

Puma is the best default app server for newly generated Rails apps and on Heroku today: it’s so easy to configure and perfectly works out-of-the-box. For today’s users it actually makes a sense to start with Puma and evaluate Passenger as your app grows and required configuration options and advanced features.

Puma runs perfectly fine with Jruby or Rubinius as implementations provides true concurrency. Developers preparing for Rails 5, admins report significant speed improvements when combining Puma with NGINX’s proxy functionality. As per the Ruby converts search for Rails servers, programmers have noticed the difference between a system supercharged with Puma and a slow stack.


Its is a simple, fast, threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications. Puma is intended for use in both development and production environments.



Unicorn, Passenger and Puma Feature Comparison

MultithreadedNoYesEnterprise Only
Slow client bufferingNoYesYes
Action CableYesYesYes
SupportOpen SourceOpen SourceOpen Source / Paid
InstallationGemGemBinary or Gem
Zero-Downtime DeploysYesYesEnterprise

As per the Passenger’s recent update addressing to speed and stability, Puma offers a lean and fast web server solution to most applications that need high concurrency. And, it always makes sense to run your own application tests and benchmarks. As per the growing ongoing support for Puma, numbers of cloud-based app servers, it has significantly refreshed version of Mongrel that is so easy to test and enjoy.

Wrap Up

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About the Author

Storyteller, Marketer, Developer, Writer, Thinker, Enabler, Rescuer, Wordsmith. I see myself as a Content Strategist. I love to write about anything and everything that pertains to the digital world, as I believe it’s an ever evolving space creative in its own way. I love facing challenges, Blogging and sharing technologies