Lead Software Engineer

Billtrust provides AI-powered B2B accounts receivable workflow and payment software across the full AR lifecycle. The Lead Software Engineer provides technical leadership within a domain-aligned cohort, leading AI-assisted development of complex SaaS features, ensuring specification and software quality, making architectural decisions, and mentoring engineers.

Responsibilities:

• Provide technical leadership within the cohort, guiding engineers in spec-driven, AI-assisted development
• Own specification quality for the most complex features, ensuring specs are comprehensive, unambiguous, and address all edge cases and non-functional requirements
• Collaborate with the Product Manager and stakeholders to translate business requirements into detailed technical specifications, and explain technical concepts to both technical and non-technical audiences
• Other duties as assigned
• Lead AI-assisted implementation for complex features, using AI coding tools such as Claude Code to generate implementations from specifications
• Review AI-generated code and peer contributions for correctness, security, performance, and architectural alignment
• Validate AI-generated tests and ensure comprehensive test coverage for complex scenarios
• Drive AI workflow standards and best practices across your cohort, advise on tools and technologies to evolve our development organization, and share learnings with other cohorts
• Create software designs that consider both current and future requirements with a DevOps mindset that will scale as our volumes increase
• Design and implement REST APIs following established patterns, and support and maintain both UI and backend services within your cohort’s domain
• Lead technical decisions and own domain expertise within your cohort
• Mentor engineers across the cohort on effective AI tool usage, spec writing techniques, and code review practices

Requirements:

• 7+ years of relevant software engineering experience, with at least 2 years designing and implementing enterprise SaaS systems
• Bachelor's degree in Computer Science (or equivalent experience), along with a firm understanding of data structures and scalable software design
• Experience coding enterprise systems at scale, with mastery of C#, C++, PHP, Java, Node.js or a similar high-level language
• Proficiency in HTML5, CSS/Sass, Angular, React, TypeScript/JavaScript, and other web technologies, with a strong ability to design and implement REST APIs
• Strong understanding of SQL and relational databases (such as SQL Server or MySQL), and proficiency in multiple persistence technologies such as NoSQL and indexed files
• Demonstrated experience working with AI coding assistants (Claude Code, Codex, Cursor, or similar), including strong code review skills to validate correctness and identify issues in AI-generated and human-written code
• Strong collaboration and communication skills, with a track record of mentoring engineers and translating business requirements into technical specifications alongside Engineering Managers, Product Managers, and cross-functional teams
• Well-honed skills in source control management using Git or similar, and experience with AWS, Azure, or a similar cloud platform
• Experience with spec-driven, agentic AI workflows where engineers delegate autonomous tasks to AI tools and provide guidance and oversight
• Experience establishing AI development practices or standards across teams
• Understanding of testable application design principles
• Track record of advising on tools and technologies that improved team productivity