If you are looking to hire a Ruby on Rails developer, you should first think about whether you actually need one. Rails is very trendy at the moment but not the best framework for every project. First, evaluate your needs and the requirements of your project in order to determine if you need a Rails developer and if so, read on to find out what to look for before hiring. 

To understand if you really need a Rails developer, ask yourself what you are looking for in the application you want to have built. There might be better solutions for your needs – for example, if you will need something similar to Trello to push updates in real-time to your clients, you might consider using Node.js as it is designed for data streaming and live updates. Similar, if you need an API or a front-end framework, Rails will not be the best solution as it is an end-to-end framework. And finally, if you need an e-commerce website with application logic, just stick to WordPress. 

But if your project does not fit in the above cases, and you need a Rails developer, here is what to look for when hiring. 

Ruby

A great Rail engineer is able to use effectively the Ruby language. To assess this, ask the developer to push up their Koans to Github and then to send you a screenshot of the final image. This will allow you to see if the developer has explored thoroughly the Ruby language. 

Testing

Ruby is a dynamic language, so testing is the best way to find out that everything stays in order while building an application. Ask the developer about their testing methodology to see if they have a solid knowledge of how to develop an in-depth test. 

Gems

Any good Rails developer will use gems to simplify their work as these are the most powerful parts of the ecosystem of Rails. Ask the developer how they will build the user authentication system – the answer should include something about gems. 

Even better is if the developer has built gems of their own or contributed to ones – this means that you have truly found a gem! 

Deployment

The deployment process is one of the most difficult parts and it is key when developing web apps. If the developer has deployed a Rails application, this is a big plus. 

General Stuff

It is important that the developer you choose will have a thorough understanding and experience in more areas when it comes to web apps development. Ask about front-end experience, favorite interfaces, and how they feel about this part of the process. 

Portfolio

Of course, an impressive portfolio of web apps built in the past is one of the surest ways to see if the developer is a good fit for your needs. Ask about their previous projects and what they are most proud of to evaluate if they are the best fit for your project.