About this role.
Capital on Tap is hiring a Senior Full Stack Engineer to help build credit-card, payments, and spend-management products for small businesses. The engineer will develop scalable .NET services and React user interfaces, own work through the full software development lifecycle, and maintain strong unit and integration testing. The position begins fully remote and will transition to a hybrid arrangement with two days per week on site in Lisbon. The role requires at least five years of hands-on experience with C#, .NET Core, SQL Server, and ideally JavaScript and React. It is a founding-engineering opportunity for the new Lisbon office, with meaningful ownership and collaboration across product, QA, and engineering.
Role DNA
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Core skills
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Sample interview questions
I would define clear domain boundaries, expose idempotent APIs, and use durable event handling with retries and dead-letter processing. I would persist transactional state in a reliable database, add observability through structured logs and metrics, and protect sensitive data through appropriate access controls and tokenization. I would also build automated unit, integration, and failure-path tests before production rollout.
I start by agreeing on acceptance criteria and API contracts with Product and QA. I cover backend business rules with unit tests, validate integrations such as persistence and API behavior with integration tests, and build focused component or end-to-end coverage for critical frontend journeys. Before release, I use code review, monitoring, and post-release checks to catch regressions quickly.
I would first use metrics, traces, and query execution plans to identify the affected endpoint and the actual query bottleneck. I would check indexes, joins, filtering, row counts, locking, parameter behavior, and any recent schema or application changes. After validating an improvement in a safe environment, I would deploy carefully and monitor latency, errors, and database load to confirm the result.
I clarify the user outcome, constraints, risks, and success measures with relevant stakeholders, then document practical options with trade-offs. For uncertain assumptions, I prefer a small proof of concept or incremental delivery path that generates evidence quickly. I communicate the decision clearly so product and engineering partners understand both the rationale and any follow-up risks.
I would focus on building trust, learning existing engineering standards, and contributing to a collaborative working rhythm from the start. I would share knowledge through thoughtful reviews, documentation, pairing, and constructive technical discussions while taking ownership of deliverables. As the team grows, I would help establish sustainable practices around quality, delivery, onboarding, and communication.
We’re Capital on Tap 👋
💳 Capital on Tap started because small businesses were underserved. Big banks were slow, their products weren’t fit for purpose, and small business owners often couldn’t access what they needed. We set out to fix that.
Today we’re a financial platform – not just a credit card company. We offer a best-in-class business credit card, SME-focused spend management platform, a savings product that hit £1 billion in funds within its first year, and a growing suite of tools and financial products that make running a small business easier.
1,000+ employees, £20bn in annual card spend, 200,000+ customers, 17,000+ Trustpilot reviews averaging 4.7 stars, and we’re profitable. We’ve done a pretty good job so far, but we’re just getting started!
We opened our first Portuguese office in Porto in autumn 2025, and in less than a year it has grown to a team of 50. Lisbon is the next step. We’re opening our first office in the city and looking for engineers to join as founding members of the team, helping shape how we build, hire and work here from day one.
🏡🏢 The role starts out fully remote. Once our Lisbon office is open, it will move to a hybrid set-up of two days a week on site.
Salary: €55,000-70,000
This is a multiple-headcount role, so please don’t be put off if you’ve seen it advertised for a while.
What You’ll Be Doing
We’re looking for Senior Full stack Engineers to help us build the best credit card and payment products for small businesses. If you’re looking for an environment where you’re given the freedom to make empowered decisions, research new technologies, and learn/share knowledge with your peers. Then keep on reading!
- You’ll build robust and scalable solutions using .Net technology
- From the first line of code to production, monitoring, and continuous improvement – you’ll own the SDLC
- You’ll craft slick, responsive user interfaces with modern JavaScript frameworks (React), making sure our products don’t just work, they feel great to use
- Teamwork makes the dream work – you’ll partner with Product Managers, QA’s, and fellow Software Engineers
- You’ll build bulletproof unit and integration tests to keep our software sharp and our users happy
- Bugs happen. When they do, you’ll be ready to troubleshoot and tweak as needed
- You’ll bridge the gap between tech speak and business goals, ensuring everyone’s on the same page and moving forward together
We’re Looking For 🔎
Required skills:
- A minimum of 5+ years hands-on experience in C#, .Net Core, SQL Server, ideally JavaScript and React also!
- Good testing practices, in both Unit and Integration testing
- Good understanding of database technologies
- Experience in using Agile development practices
- A passion for learning new skills and technologies
- A proactive, supportive, and collaborative team player
Our Tech Stack
- Backend: C#, .Net, .Net Core
- Frontend: React, JavaScript
- Mobile: Flutter, Dart
- Databases: SQL Server, MongoDB
- Cloud: Azure & GCP
Interview Process 🤝
- First stage: 30-minute intro, CV review, and values with a Talent Partner
- Second stage: 45-minute “Tech Chat” with a Team Manager
- Final stage: 90-minute Code Pairing + 30-minute Values Interview
Diversity & Inclusion 🌈
We welcome, consider and encourage applications from anyone who shares our commitment to inclusivity. Join us in creating a space where authenticity thrives, and everyone can do their best work.
Great Work Deserves Great Perks
Check out our benefits:
🏥 Private Healthcare through AdvanceCare
🎁 Anniversary Rewards (€280, €570, €860, 4-week fully paid sabbatical)
🏖️ 36 days holiday (inclusive of public holidays with public holidays carried over if they fall on a weekend)
📖 Annual Learning and Wellbeing Budget
💬 6 free therapy sessions per year
🍫 Free drinks and snacks in our offices
Other Info
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✔️Keep updated on new job opportunities by following us on Linkedin.
📧Email careers@capitalontap.com if you have any questions.
Excited to work here? Apply!
If you’d like to progress your career within our fast growing, profitable fintech then click apply and we will aim to get back to you within 3 working days (during busy periods this could take up to 5 working days.)
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