Backend Software Engineer, Core App

Role Overview

As a Backend Software Engineer (Core App) on OnePay’s Core App team, you will build backend systems that directly power mobile and web user experiences.

Responsibilities

• Design, build, and ship backend services that support user-facing features across mobile and web.
• Collaborate with frontend engineers, product managers, designers, and data partners.
• Lead backend technical planning and contribute to architecture decisions to improve scalability, reliability, and performance.
• Proactively identify backend optimizations and system improvements that enhance user experience.
• Build and maintain technical documentation to support a growing, distributed engineering org.

Requirements

• 5+ years of professional experience building and scaling backend systems in consumer technology or fintech.
• Experience designing and operating distributed systems, APIs, and data flows that support user-facing applications.
• Familiarity with message brokers and event-driven systems, plus caching and performance optimization.
• Ability to lead technical execution, mentor engineers, and deliver high-quality work.
• Strong drive and proactivity (builder/executor mindset).

Nice to Have / Tools & Tech

• Familiarity with functional programming concepts; OnePay uses fp-ts.
• Node/TypeScript experience is relevant, though the posting indicates you can ramp up on new stacks.

Interview Process

• Initial interview with Talent Partner
• Technical/Hiring Manager interview
• Team interview
• Executive interview
• Offer