Senior Software Engineer - Web Application & Developer Experience

We're looking for a Senior Software Engineer to help build and evolve the systems and APIs that power Runware's Web App and Developer Experience (DevEx). You'll work closely with backend engineers, frontend engineers, Product, Design and other teams to build reliable internal and developer-facing APIs and functionality that make complex AI infrastructure simple to use. You'll take ownership of backend work from understanding requirements and technical constraints through to implementation and delivery, contributing to the quality, reliability and evolution of the Web App and its supporting APIs. This role combines technical depth with product thinking and collaboration. You'll be expected to work autonomously, contribute to technical decisions and help turn ambitious ideas into robust production systems. What you'll do Build and maintain internal and developer-facing APIs and services that power the Web App and developer experienceDevelop and evolve public API functionality, including task types, validation, routing and WebSocket/REST behaviourOwn and maintain the Admin API and panel as an internal platform used across RunwareWork with usage, billing and customer data to ensure accuracy and reliability, including StripeInvestigate and resolve production issues and security vulnerabilities affecting the Web App and its APIsWrite, test and review clean, maintainable code, contributing to strong engineering practices and code qualityWork with Product, Design and engineering teams to clarify requirements, identify dependencies and define well-scoped technical solutionsContribute to technical decisions, work across frontend and backend boundaries where appropriate, and collaborate with the wider Backend team where specialist knowledge or shared systems are involved Requirements Strong experience building backend systems and APIsStrong programming experience in one or more backend languages, with the ability to quickly learn and work effectively in new languages and technologiesExperience building reliable, maintainable and well-tested production systemsGood understanding of API design, asynchronous workloads and distributed systems conceptsStrong engineering fundamentals around security, reliability and performanceStrong communication and collaboration skills, with the ability to work effectively across engineering, Product and DesignStrong ownership and autonomy, with good judgement around when to involve othersComfortable using AI-assisted development tools and agents to improve productivity, while understanding their limitations and maintaining responsibility for the quality, security and correctness of the resulting code Nice to have Experience with PHP, Symfony and/or DoctrineExperience with WebSocketsExperience building public APIs or other developer-facing productsExperience with usage-based billing, credits or financial dataExperience contributing to architectural decisions and mentoring other engineers Benefits We're a remote-first collective, meeting in person twice a year to plan, brainstorm, celebrate wins, and enjoy some face-to-face time. We have core hours for cooperative working and calls, but outside of that your calendar is yours. Work the hours that let you perform at your peak while also building a healthy life. Our release cycles are fast and intense, but they're followed by real downtime. After big pushes we expect the team to unplug, recharge, and come back ready & stronger than ever for the next leap. Generous paid time off - vacation, sick days, public holidays Meaningful stock options - share in the upside you create Remote-first setup - work from home anywhere we can employ you Flexible hours - own your schedule outside core collaboration blocks Family leave - paid maternity, paternity, and caregiver time Company retreats - twice-yearly gatherings in inspiring locations