Ruby on Rails Developer Cover Letter Example
A worked example for a ruby on rails developer application. The Rails version you last shipped on, and whether the codebase was mature or greenfield.
Nadia Brennan
Head of Engineering
Northbridge Software
Dear Ms. Patel,
I am applying for the Ruby on Rails Developer position at Northbridge Software. I have spent 8 years in this field, most recently as Senior Ruby on Rails Developer, and the work described in your posting is close to what I do now.
The result I would point to first is that I rebuilt the Sidekiq billing pipeline around idempotent workers, cutting job failures 82% and ending manual replays. Day to day my work centres on Ruby, Ruby on Rails and PostgreSQL, which maps directly onto what this role calls for. I have attached my resume, which sets out the rest in the same terms.
[Add one genuine, specific reason you want to work at Northbridge Software — a product, a recent announcement, or how the team works. One real sentence beats a paragraph of praise.] I would welcome the chance to talk about where I could be most useful.
Thank you for your time and consideration.
Adapting this for a ruby on rails developer application
Paragraph one: the role, and why you are credible
Name the exact job title and where you saw it, then one line establishing that you already do this work. Skip "I am writing to express my keen interest" — it spends a sentence saying nothing.
Paragraph two: one achievement, with a number
Choose the achievement most relevant to the posting rather than the one you are proudest of, and attach a figure: a percentage, an amount, a volume, a timeframe. One specific result beats three general claims and gives the interviewer something concrete to ask about.
What this field is judging behind the words
The Rails market is small, senior-weighted and well connected, so referrals matter more than in larger language communities. Processes usually include a take-home or a pairing session in a real codebase rather than abstract puzzles, reflecting the fact that most of the work is extending something that already exists. Remote roles are disproportionately common. Employers screen hard for test discipline and for comfort navigating code written by people long gone.
Paragraph three: why this employer
This is where most letters fail. "I admire your commitment to excellence" could be sent to anyone. Name something real — a product, a recent announcement, how the team works, a market they are moving into — and connect it to your own experience. If you genuinely cannot find anything specific to say, that is worth noticing before you apply.
Mistakes that cost ruby on rails developer candidates
- Treating a bootcamp Rails project as equivalent to production experience in a market that is hiring mostly seniors
- Omitting upgrade and maintenance work, which is precisely what most Rails employers are trying to staff
- Naming gems without saying what you did with them; the gem list is not the accomplishment
Those are resume mistakes, but they apply to the letter for the same reason: both documents are read by someone deciding quickly whether you understand the job.
What this role needs on paper
No Rails or Ruby certification exists that anyone in hiring recognises, and none is expected. Degrees are inconsistent across the community and rarely decisive. The functioning credentials are open source contributions, a visible history in the ecosystem, and production experience on an application with real users behind it. Bootcamp graduates find this a difficult first market precisely because so few junior seats exist.
Where this leads if you get it
Mid to senior, then typically technical lead or staff engineer inside one product, or consulting — Rails consultancies are a well-established route. Some developers move sideways into platform work as their applications outgrow the monolith.
Before you send it
Reread the letter for the previous employer's name — reusing a letter and leaving the old company in it is the most common fatal typo there is. If you are applying in the UK, the National Careers Service sets out what employers there expect alongside a CV. Then run the resume that accompanies it through our free ATS checker. The letter gets you read; the resume is what the applicant tracking system scores.
Ruby on Rails Developer Cover Letter Questions
What should a ruby on rails developer cover letter say?
Three short paragraphs: the role you are applying for and why you are credible, your single strongest relevant achievement with a number attached, and one genuine reason you want this employer. Anything past one page usually goes unread.
Do employers hiring ruby on rails developers actually read cover letters?
It varies by employer and it is rarely the deciding document. It matters most for competitive roles, career changes and gaps, where a resume alone handles the context badly. When the application asks for one, always include it.
What does this field want to see in the letter?
The Rails version you last shipped on, and whether the codebase was mature or greenfield. Say it in the first two lines rather than saving it for the second page.
Should I repeat my resume in the letter?
No. The resume already lists what you did. The letter answers the two questions a list cannot: why this role, and why this employer. Pick the achievement most relevant to the posting and give it context.
Where does this career usually go from here?
Mid to senior, then typically technical lead or staff engineer inside one product, or consulting — Rails consultancies are a well-established route. Some developers move sideways into platform work as their applications outgrow the monolith.
How long should it be?
Roughly 250 to 350 words on one page. The three-paragraph discipline forces you to lead with what matters instead of restating the resume.
Can I copy this example?
Use the structure and the job each paragraph does, but write your own content. The employer and candidate here are fictional, and a letter describing work you did not do will not survive an interview.
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