Staff Software Engineer, Platform & API

Location: Florida (Miami preferred). Hybrid. About the Role Our hiring partner is looking for a high-agency Staff Software Engineer to join the Platform team and own the API surface that partners and customers build on. The public API is a product in its own right, used by accounting firms, payroll providers, and platforms to integrate tax payments into their software. This staff-level role spans the platform rather than a single feature area. You will work across data models, services, and developer-facing surfaces, shape standards and architectural patterns, write substantial production code, and help other engineers grow. Key Responsibilities

• Own the design and evolution of the public API, including resource modelling, versioning, pagination, idempotency, errors, authentication, backward compatibility, and deprecation.
• Treat developer experience, documentation, clarity, and predictability as first-class product requirements.
• Lead significant platform-system designs and align technical direction with the broader roadmap.
• Make and document trade-offs across performance, scalability, security, correctness, reliability, and maintainability.
• Build complex features across data models, services, shared libraries, and developer-facing surfaces.
• Own platform services in production, lead incident investigation, and strengthen observability, alerting, and testing.
• Apply a security-first mindset to authentication, authorization, tenancy isolation, and data handling.
• Mentor engineers and contribute to engineering culture, hiring, onboarding, and standards.

Who You Are

• 8+ years of software engineering experience designing and operating production systems at scale.
• Proven experience building API products consumed by external developers or partners.
• Deep hands-on proficiency with C# and .NET plus modern JavaScript or TypeScript.
• Demonstrated ownership of non-trivial systems from architecture through production.
• Strong systems judgment and a record of technical leadership, alignment, and mentoring without relying on formal authority.
• Excellent communication and the ability to explain trade-offs to engineers, executives, and partners.
• Experience working in a high-growth or fast-paced technology environment, with the ability to adapt quickly as teams, products, and priorities evolve.
• Based in or willing to relocate to Florida, with Miami preferred.

Nice to Haves

• Payments, banking, financial infrastructure, tax, compliance, or another correctness-critical domain.
• Developer tooling such as CLIs, SDKs, or MCP servers.
• AWS, CI/CD, secure coding, threat modelling, Blazor, and AI/LLM-assisted development.
• Interest in growing into engineering management over time.

Why Join Us Own the API that partners build products on, influence architecture across teams, and work on mission-critical fintech infrastructure where correctness genuinely matters.