Senior Software Engineer (SWE 3)

About Downstream

Downstream is a marketplace platform transforming the waste and construction industries from the ground up. We're on a mission to bring simplicity, transparency, and sustainability to two of the most essential — but often overlooked — sectors of our economy.

We make it easy for contractors, builders, and businesses to find and book critical services like dumpster rentals, hauling, site services, and equipment — all in a few clicks. No endless calls, no confusing pricing, no waiting around. Our platform connects customers with vetted, reliable providers so they can get what they need, when they need it.

We're not just about convenience — we're about impact. By streamlining logistics and digitizing the supply chain, we're helping reduce waste, cut emissions, and build a cleaner, more sustainable future. Let's build better, together.

About the role

We're looking for a Senior Software Engineer to lead the delivery of significant product features and systems across the Downstream marketplace. You'll make sound technical decisions, solve ambiguous problems, and build production-grade Django services and agentic AI capabilities. You'll help determine how intelligent systems reason, plan, and execute multi-step tasks across logistics, pricing, and supplier matching, while raising engineering quality and mentoring the team.

What you'll do

• Lead the design, development, and operation of major Django applications, APIs, data models, and marketplace services
• Architect and implement production-grade agentic AI systems, including multi-agent workflows that reason, plan, use tools, and execute multi-step tasks
• Select and integrate appropriate AI tools and frameworks, including LangChain, LangGraph, OpenAI, Hugging Face, or custom orchestration
• Establish reliable patterns for agent state, tool permissions, context management, evaluation, observability, fallbacks, and human review where appropriate
• Partner cross-functionally to embed intelligent decisioning and automation into logistics, pricing, supplier matching, and marketplace operations
• Own technical decisions and tradeoffs across performance, reliability, security, cost, and delivery speed
• Drive complex features from concept through production, including technical planning, implementation, rollout, and iteration
• Review designs and code, mentor junior and mid-level engineers, and unblock the team on difficult technical problems
• Collaborate with product and design to shape scope, sequencing, and the technical roadmap

Role specifics

• Ownership: leads major features and systems, including technical direction and production outcomes
• Architecture: designs service boundaries, API contracts, data models, and integration patterns that can evolve with the marketplace
• AI responsibility: delivers agentic systems beyond basic API wrappers, with measurable quality, reliability, safety, and operational controls
• Technical leadership: sets a high bar for code quality, testing, documentation, observability, and engineering judgment

Who you are

• You have substantial experience building and shipping Django/Python applications and production APIs
• You can lead system design across REST APIs, PostgreSQL or similar relational databases, and distributed service integrations
• You've designed or materially contributed to LLM-powered systems involving reasoning, planning, tool use, or multi-step workflows
• You have hands-on experience with one or more AI frameworks or platforms such as LangChain, LangGraph, OpenAI, Hugging Face, or custom orchestration
• You understand production concerns for AI systems, including evaluation, latency, cost, failure handling, observability, and data security
• You can navigate ambiguity, make pragmatic technical decisions, and move work from concept to production
• You're an effective mentor and cross-functional partner; construction tech, logistics, rentals, or marketplace experience is a plus

Compensation

$125,000–$160,000 per year (Series A compensation band).

Benefits

Downstream is an equal opportunity employer. We consider all applicants for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, national origin, age, disability, genetic information, veteran status, or any other protected status under applicable law.

• Medical, dental, and vision insurance
• 401(k) with a company match
• Company equity — be an owner in what we're building
• Paid time off, paid holidays, and floating holidays
• Parental and bereavement leave