Senior Backend / Fullstack Engineer (Go)

FunnelFox is a no-code platform that helps app developers grow revenue through web2app funnels. Launched two years ago as Adapty’s new project, it’s already showing impressive growth. Marketers and product managers can build, launch, and optimize funnels in hours instead of months, all without writing a single line of code.

We are looking for a Senior Fullstack Engineer to join our Payments team. This team owns everything related to payment infrastructure inside FunnelFox: checkout flows, payment provider integrations, and the systems that make payments reliable, scalable, and flexible for our clients.

This is a highly autonomous role in a fast-moving startup environment. You will work on complex integration-heavy problems, collaborate closely with product and engineering, and help shape technical solutions in areas where requirements are often evolving rather than perfectly predefined.

In this role, you will:

• Build and improve integrations with payment service providers (PSPs) and external payment systems.

• Work on checkout infrastructure, payment flows, and backend reliability.

• Design and maintain backend logic for integrations, async processes, webhooks, and related systems.

• Participate in technical discovery and decomposition of business requirements.

• Collaborate closely with Product, Support, and Engineering on shaping solutions, not just implementing tickets.

• Investigate and resolve production and payment-related issues.

• Contribute to improving internal engineering quality, reliability, and scalability across the payments domain.

• Work in an environment with high ownership, evolving priorities, and a strong focus on practical impact.

You will be a great fit, if you have:

• Strong backend engineering experience.

• Solid experience with payment systems, PSPs, or external integrations.

• Experience working with APIs, webhooks, async flows, and integration-heavy architectures.

• Good understanding of distributed systems and backend scalability challenges.

• Experience working in startup or fast-changing environments.

• Ability to work autonomously and navigate partially defined requirements.

• Strong ownership mindset and pragmatic engineering judgment.

• Ability to communicate clearly and collaborate cross-functionally.

Nice to have:

• Experience with Go.

• Experience with multiple payment providers.

• Experience with frontend development or fullstack environments.

• Experience working on B2B SaaS or growth-related products.

• Experience with observability, monitoring, or incident handling.

• Interest in product thinking and business impact, not only implementation.

What you may expect from working with us:

• Flexible remote work: Work from anywhere with a schedule that fits your life. Our core team operates in Europe, and we welcome candidates worldwide using Deel.com.

• High ownership and real impact: Engineers actively influence product and technical decisions, not just implementation details.

• Fast-moving startup environment: We value speed, autonomy, and practical problem-solving over rigid corporate processes.

• Direct communication: We keep things simple and transparent, ensuring you focus on what matters most — getting things done.

• Professional Support: We provide a monthly budget that you can allocate based on your personal and professional priorities — including language learning, professional development, mental health support, sports, or health insurance.