Senior Software Engineer - Backend

About ZAR

ZAR is innovating on financial infrastructure in emerging markets by combining the power of blockchain and stablecoins with practical, user-friendly financial products. We're creating a platform that makes digital payments accessible, secure, and seamless for everyone. Our mission is to bridge the gap between traditional finance and Web3, delivering real value to people living in the most under-served countries.

We're a team that values craftsmanship, customer obsession, and systems thinking. We believe great software is built by engineers who care deeply about both code quality and the people using their products.

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The Challenge

We're at a critical inflection point. Our user base is growing rapidly (200k+), and we need to scale our backend infrastructure to match. But this isn't just about handling more traffic—it's about building systems that are reliable, maintainable, and elegant.

We're looking for a Senior Software Engineer who can help us level up our backend architecture. Someone who sees the big picture, thinks in systems, and writes code that other engineers love to work with. You'll be joining a team that's committed to doing things right, not just fast.

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What You'll Do

You'll be a key technical leader on our backend team, responsible for designing and building the systems that power parts of ZAR's financial platform. This role is about more than just writing code—it's about designing solutions that scale, mentoring engineers, and establishing patterns that define how we build software.

Core Responsibilities

Build Robust, Scalable Systems
You'll design and implement backend services that handle financial transactions, user authentication, blockchain integrations, and real-time data processing. These systems need to be rock-solid—our users depend on them for their financial lives.

Champion Code Quality
You'll establish and enforce engineering best practices across the team. This means writing clean, testable code, conducting thorough code reviews, and creating documentation that helps the team understand complex systems. You'll be the person others look to for guidance on how to do things right.

Think in Systems, Not Scripts
We need someone who can see the forest and the trees. You'll identify architectural patterns, eliminate technical debt, and refactor legacy code into maintainable, well-structured systems. You understand that good architecture makes future development faster, not slower.

Own Critical Features End-to-End
From API design to database schema to deployment, you'll take full ownership of major features. You'll work closely with product managers, designers, and mobile engineers to deliver solutions that delight users while maintaining technical excellence.

Mentor and Elevate the Team
You'll help other engineers grow by reviewing their code, pairing on complex problems, and sharing your knowledge. You'll create a culture where quality matters and learning is continuous.

Optimize for Performance and Reliability
You'll monitor system performance, identify bottlenecks, and implement solutions that keep our platform fast and reliable. You'll build observability into everything you create so we can understand and improve our systems over time.

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What We're Looking For

We're not looking for someone who just checks boxes on a resume. We're looking for an engineer who cares—about code quality, about users, about building things that last.

Must-Haves

Deep Backend Engineering Experience
You have 5+ years of experience building production backend systems. You've seen systems at scale, dealt with complex data models, and know how to design APIs that stand the test of time.

Strong Systems Thinking
You naturally think about how components fit together. You can identify patterns, spot architectural problems before they become crises, and design solutions that are both elegant and pragmatic.

Commitment to Code Quality
You write code that's clean, well-tested, and maintainable. You believe in code reviews, automated testing, and documentation. You understand that code is read far more often than it's written.

Customer-Centric Mindset
You don't just build features—you solve problems for real people. You think about edge cases, error handling, and user experience. You understand that great engineering means nothing if users can't rely on your work.

Excellent Communication Skills
You can explain complex technical concepts to non-technical stakeholders. You write clear documentation, give thoughtful code reviews, and collaborate effectively with cross-functional teams.

Ownership and Accountability
You take pride in your work and stand behind it. When something breaks, you jump in to fix it. When something could be better, you make it better. You don't wait for permission to do the right thing.

Nice-to-Haves

- Ruby on Rails expertise - We're a Rails 8 shop, and experience with modern Rails patterns is a huge plus
- Financial systems experience - You've built systems that handle money, transactions, or sensitive data
- Blockchain/Web3 knowledge - Familiarity with Solana, smart contracts, or crypto wallets
- DevOps skills - Experience with AWS, Docker, CI/CD pipelines, and infrastructure as code
- API design expertise - You've designed RESTful APIs that are a joy to use
- Performance optimization - You know how to profile, benchmark, and optimize slow code
- Open source contributions - You've contributed to or maintained open source projects

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## Our Tech Stack

You'll be working with modern, production-grade technologies:

Backend
- Ruby on Rails 8 (latest and greatest)
- PostgreSQL 17 (our primary database)
- Redis (caching and background jobs)
- Sidekiq (background job processing)

Infrastructure
- AWS (cloud infrastructure)
- Docker (containerization)
- GitHub Actions (CI/CD)
- Solana (blockchain integration)

Tools & Services
- ActiveAdmin (internal admin tools)
- Sentry (error tracking)
- Linear (project management)
- GitHub (Git)

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What Makes This Role Special

Real Impact
You'll be building financial infrastructure that directly affects people's lives. Your code will process real transactions, secure real money, and enable real financial access for users who need it.

Technical Ownership
You'll have significant autonomy to make architectural decisions and shape how we build software. We trust our senior engineers to do what's right, not just what they're told.

Quality-First Culture
We're committed to building things the right way. We value thoughtful design over quick hacks, maintainability over speed, and long-term thinking over short-term wins.

Growth Opportunity
We're a growing startup with ambitious goals. As we scale, there will be opportunities to lead teams, define technical strategy, and shape the future of the company.

Remote Flexibility
Work from anywhere. We're a remote-first company that values results over hours logged. We trust you to manage your time and deliver great work.

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Our Values

Own It

Take full responsibility for everything on your plate, from conception to completion. Don't stop at hand-offs, QA, or deployment. Everyone on the team is a product owner, delivering value that will impact the lives of millions of people globally.

Automate It

Don't allow yourself to become a bottleneck in progress. Identify and pursue opportunities to automate and streamline processes, freeing up time and resources for high-value work that requires human expertise.

Communicate Clearly

In a remote-first company, exceptional written and verbal communication is paramount. With limited opportunities to interact, each exchange must be extra effective.

Get Granular

Mastery and depth of knowledge in one's specific field, regardless of role or department. We hire experts, not functions—people who bring deep expertise rather than just filling a slot on an organizational chart.

Make Thoughtful Decisions

Team members must take ownership of their responsibilities, sometimes making critical business decisions. We expect evidence of careful consideration behind these decisions.

Move Fast

We value quick incremental progress. Breaking larger problems into actionable steps and accomplishing them is key to making progress and testing hypotheses.

Challenge Assumptions

Strong ideas withstand criticism rather than being protected from it. We seek people who can thoughtfully critique underlying assumptions behind business and product decisions to achieve better outcomes.

Drive Outcomes

We focus on results, not working hours. Understand the company's shared vision or goal by asking questions and seeking clarity, then deliver meaningful outcomes.

Be Dynamic

As an early-stage company in a nascent industry, we need team members who thrive amid uncertainty by remaining flexible and creative in their approach to work and problem-solving.

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What We Offer

Competitive Compensation
We offer competitive salary and equity. We believe in rewarding great work and sharing in our success.

Health & Wellness
Comprehensive health insurance, mental health support, and wellness stipends.

Professional Development
Budget for conferences, courses, books, and anything else that helps you grow as an engineer.

Modern Tools
We provide the best tools for the job—whatever hardware, software, or services you need to do your best work.

Flexible Time Off
Generous PTO policy because we know that rest and balance make better engineers.

Remote-First Culture
Work from anywhere with flexible hours. We care about your output, not your location or schedule.

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#The Interview Process

We respect your time and want to make this process as transparent as possible:

1. Initial Call (30 min) - Get to know each other, discuss your background and our needs
2. Technical Discussion (60 min) - Deep dive into your past work, architectural decisions, and problem-solving approach
3. Code Review Exercise (async) - Review a real pull request from our codebase and provide feedback
4. System Design Interview (90 min) - Design a system together, discuss trade-offs and architecture
5. Team Fit Conversation (45 min) - Meet the team, discuss culture and collaboration
6. Offer - If it's a mutual fit, we'll make you an offer

We aim to complete this process within 2 weeks and will keep you updated at every step.

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How to Apply

If this sounds like the right challenge for you, we'd love to hear from you.

Please send us:
1. Your resume or LinkedIn profile
2. A brief note (a few paragraphs) telling us:
- Why you're interested in ZAR
- A system you're proud of building and why
- What "code quality" means to you
3. Links to your work (GitHub, blog posts, open source contributions, etc.)

Apply at: sebastian@zarpay.app