Senior Software Engineer, Full Stack

Postscript is the AI messaging platform trusted by 20,000+ Shopify brands — including Brooklinen, Ruggable, True Classic, and Dr. Squatch. With a mission to make SMS your number one revenue driving channel, we built the best-in-class SMS marketing platform and launched revenue-driving AI features not available on any other platform. And we're just getting started. Backed by Greylock and Y Combinator, fully remote since 2018. As a Senior Fullstack Engineer at Postscript, you'll be a high-ownership contributor to one of our core product or platform teams — owning meaningful systems end-to-end, driving technical quality, and helping shape how we build across the organization. Our engineering teams operate at the intersection of scale and product velocity, which means you'll be working on distributed systems that matter to the business while also influencing the technical standards that allow Postscript to grow sustainably. This is a high-autonomy role for engineers who are energized by ambiguity, take genuine ownership of their work, and bring a strong point of view on how to build things well — without sacrificing speed or pragmatism. AI isn't a nice-to-have here — it's central to how we work. We expect our engineers to be active practitioners of AI-first development: fluent with the latest agentic coding tools, curious about what's emerging, and constantly pushing the boundary of what's possible with AI in their day-to-day craft. If you're the kind of engineer who's already experimenting with new models and tooling before anyone asks you to, you'll feel at home here. As a senior engineer at Postscript, you’ll no longer be only writing code but orchestrating it. This position is fully remote and can be based in the US or Canada. Primary Duties Take deep ownership of systems and product areas on your team — becoming the go-to technical expert for what you own Independently investigate, design, and execute solutions across distributed systems with a high degree of ambiguity Architect, build, and maintain highly available, scalable REST APIs and backend services for internal and external use Drive system decoupling, modularization, and technical debt reduction — improving long-term maintainability without blocking near-term delivery Build agentically as your default: run multiple autonomous agents and worktrees in parallel (5+ is the benchmark), own the output, and keep a steady queue of aligned work moving Stay at the forefront of emerging AI tooling and practices, bringing new techniques back to the team and helping raise the floor for how Postscript engineers work Contribute to how we think about integrating AI into our systems and workflows — not just using AI tools, but helping shape where and how AI creates leverage across the engineering org Collaborate cross-functionally with product, data, and go-to-market teams — communicating clearly and proactively in an async-first environment Identify and eliminate single points of failure, improving system resilience and knowledge redundancy across your team Improve how engineering gets done: bring better tools, fix workflow friction, build internal utilities when the leverage compounds What We'll Love About You 6+ years of experience building large-scale backend systems and APIs You are an active, daily user of AI coding tools and are using them to maximize your output — Claude Code, Cursor, Copilot, or equivalent — and can speak concretely to how they've changed your output and your workflow Tech stack: Python, Go, React, and TypeScript; experience with Kubernetes, AWS, Datadog, and relational/NoSQL databases. You follow the AI tooling landscape closely: new model releases, emerging agentic workflows, and evolving best practices aren't things you catch up on eventually — they're things you're tracking in real time You think critically about AI output — you know where it accelerates you, where it introduces risk, and how to verify what it produces You are able to context switch extr