Senior Full Stack Engineer

Spectrum Search is partnered with an early-stage AI-enabled financial technology company building software for complex B2B payment and revenue workflows. The company is looking for a product-focused engineer to take end-to-end ownership of customer-facing systems across backend, frontend and AI-enabled functionality.

This is a full-time engineering role within a small, highly collaborative product team. Engineers work directly across product definition, architecture, implementation, testing and measurement, with significant ownership over what reaches production.

The environment is highly iterative and AI-enabled. The team uses modern AI development tooling as part of its day-to-day engineering workflow, while engineers remain responsible for technical decisions, system quality and production outcomes.

You will build and evolve systems supporting payment processing, financial workflows, integrations and AI-powered product capabilities. The role is backend-leaning but genuinely full stack, requiring engineers who are comfortable moving between application logic, databases, APIs and React-based user experiences.

You will also work directly with customer signals and feedback, helping translate real operational problems into well-scoped technical solutions.

• Design, build and operate production-grade payment and financial workflow systems
• Develop secure APIs and integrations with third-party enterprise platforms
• Build full-stack product features across backend services, PostgreSQL and React
• Develop LLM-powered workflows and agentic AI features for complex operational processes
• Create evaluation frameworks, observability and guardrails for AI functionality in production
• Build and maintain data pipelines processing high volumes of financial records
• Own features from initial customer requirements through specification, delivery and measurement
• Contribute to system architecture, technical conventions, code reviews and engineering quality

• Proven experience as a backend-leaning full-stack software engineer, with strong recent ownership of production systems and user-facing features
• Strong backend expertise using an MVC framework such as Ruby on Rails, Django or Spring Boot
• Advanced experience with SQL databases such as PostgreSQL
• Ability to deliver across backend, frontend, database schema and automated testing without relying on functional hand-offs
• Experience working in an environment with rapid product iteration and meaningful individual ownership
• Strong product engineering mindset with experience taking responsibility beyond initial feature launch
• Comfortable engaging with users and customer feedback to inform technical decisions
• Active use of AI-assisted development tooling in day-to-day engineering workflows
• Strong ability to decompose product requirements into clear, scoped engineering work

• Experience shipping production-grade agentic AI or LLM features
• Experience with AI evaluation systems, A/B testing or multi-arm bandit approaches
• Product engineering experience within fintech, payments or billing
• Experience with Ruby on Rails, React, AWS or Terraform

This is a full-time, remote position for candidates based in the US. Quarterly in-person off-sites are required. Visa sponsorship is not available for this position.