A software engineer cover letter is read fastest when it does the opposite of what most candidates do — instead of restating the resume in prose, it should reference one specific project or problem that maps directly to what the job posting is asking for.
Example cover letter
I saw your posting for a Backend Engineer focused on scaling your payments infrastructure, and it's almost exactly the problem I spent the last year solving at my current company — migrating a monolithic billing service to microservices without a minute of downtime.
At my current role, I led that migration end-to-end: designing the service boundaries, building the CI/CD pipeline that let us deploy safely twelve times a day, and mentoring two junior engineers through their first production incidents. The result was a 74% drop in average API response time and a system that now handles 2M+ daily requests without the on-call pages that used to wake me up weekly. I'm looking for a team solving a similarly gnarly scaling problem, and your job posting's mention of moving to event-driven architecture is exactly the kind of work I want to be doing next.
I'd welcome the chance to talk through how I approached the migration and how it might apply to what your team is building. I'm available for a call anytime this week.
Common mistakes to avoid
- Opening with "I am writing to apply for..." instead of a specific reason the role caught your attention.
- Restating the resume's bullet points verbatim instead of adding context — the letter should explain the 'why,' the resume covers the 'what.'
- Writing more than one page — for engineering roles, a tight 3-paragraph letter reads as more confident than a long one.
Frequently asked questions
Should a software engineer even bother with a cover letter?
If it's optional, write a short one anyway when you have a genuinely relevant project to reference — it costs the reader 30 seconds and can be the tiebreaker between two similar resumes.
Is it okay to mention specific technologies from the job posting?
Yes — naming the specific stack or problem from the posting (not just "your tech stack") signals you actually read it, which most applicants skip.