Senior Software Engineer, Backend (Batch Infrastructure)

About the Team DoorDash’s GenAI Platform team sits within Machine Learning Platform and builds the shared infrastructure that helps DoorDash, Wolt, and Deliveroo teams safely bring GenAI-powered products, agents, automation, and personalization to production. Our mission is to increase the velocity of business impact from GenAI. A central pillar of that work is running frontier open-weight LLMs and VLMs (such as GLM, Qwen, Kimi, and DeepSeek) ourselves — real-time GPU serving, high-throughput batch inference, and fine-tuning on autoscaling GPUs — delivering large cost and latency wins (for example, a billion embeddings produced roughly 20× cheaper and visual models served roughly 72% cheaper). We also own core platform surfaces including the LLM Gateway, Agent Gateway, evals infrastructure, guardrails, and cost attribution. About the Role You will join a small, high-leverage team building production infrastructure for Generative AI at DoorDash, leading the design and architecture of our open-weights model platform spanning inference and fine-tuning: real-time GPU serving, high-throughput batch inference, and model fine-tuning. You’ll set technical direction across model serving and inference engines, fine-tuning and training pipelines, GPU autoscaling and utilization, batch pipelines, backend services, and observability, and mentor engineers as you go. This role is ideal for a senior engineer who enjoys owning ambiguous, high-impact systems and pushing the cost/performance frontier of GPU inference and fine-tuning in a fast-moving technical area where product needs, model capabilities, vendor ecosystems, and cost/performance tradeoffs are evolving quickly. You’re excited about this opportunity because you will… Lead the design of infrastructure that helps DoorDash teams move GenAI ideas from prototype to production, increasing the velocity of business impact from AI across the company. Own and evolve our open-weights serving stack — real-time GPU endpoints, high-thr

Why join us Brex is the intelligent finance platform that enables companies to spend smarter and move faster in more than 200 markets. By combining global corporate cards and banking with intuitive spend management, bill pay, and travel software, Brex enables founders and finance teams to accelerate operations, gain real-time visibility, and control spend effortlessly. Brex’s AI-native automation and world-class service eliminate manual expense and accounting tasks for customers so they can focus on what matters most. Tens of thousands of the world's best companies run on Brex, including DoorDash, Coinbase, Robinhood, Zoom, Plaid, Reddit, and SeatGeek. Working at Brex allows you to push your limits, challenge the status quo, and collaborate with some of the brightest minds in the industry. We’re committed to building a diverse team and inclusive culture and believe your potential should only be limited by how big you can dream. We make this a reality by empowering you with the tools, resources, and support you need to grow your career. Engineering at Brex Engineering at Brex is about building systems that scale with speed and intention. Our teams span Software, Data, Security, and IT, and operate with high autonomy and deep collaboration. We tackle hard technical problems, own our outcomes, and push for excellence at every level — from architecture to deployment. It’s an environment where engineering is a craft, and builders become leaders. What you’ll do As an engineer at Brex, you will help develop new products from concept to launch, whether for a 5-person startup or a 5,000-person-strong enterprise. We’re looking for folks with an interest in building products and tools, and who are comfortable in dealing with lots of moving pieces. You’ll be building customer-facing products that will drive direct business impact and shape our long-term technical vision with a high-quality bar. You'll have the opportunity to learn and push the frontier of providing the best fin

At Affirm, we exist for the moments that matter—giving people a clear, predictable way to pay over time, with no hidden fees, no surprises, and no tradeoffs on what matters most. The Engineering team builds systems that power Affirm’s mission. We take pride in our craft, building reliable, performant, and scalable solutions that touch every part of the business. Whether we’re enabling new ways to pay, ensuring our platforms can scale to the most demanding levels in the industry, or developing seamless servicing experiences, our focus is on solving complex problems through exceptional engineering. The Powered by Affirm (PBA) team builds the APIs and solutions that power all of Affirm’s integrations with Enterprise Merchants and Partners. We create and manage the APIs and tools that drive checkout and merchant onboarding, and we collaborate with stakeholders to design and build custom end-to-end integrated solutions. What You'll Do · You will be responsible for owning and delivering quarterly goals for your team, leading engineers on your team through ambiguity to solve open-ended problems, and ensuring that everyone is supported throughout delivery. · You will support your peers and stakeholders in the product development lifecycle by collaborating with product management, design & analytics by participating in ideation, articulating technical constraints, and partnering on decisions that properly consider risks and trade-offs. · You will proactively identify project, process, technology or business issues, advocate for them, and lead in solving them. · You will support the operations and availability of your team’s artifacts by creating and monitoring metrics, escalating when needed, and supporting “keep the lights on” & on-call efforts. · You will foster a culture of quality and ownership on your team by setting or improving code review and design standards for your team, and advocating for them beyond your team through your writing and tech talks. · You wi

At Affirm, we exist for the moments that matter—giving people a clear, predictable way to pay over time, with no hidden fees, no surprises, and no tradeoffs on what matters most. The Partner Merchant Interfaces - Integration team within Decisions Foundations is growing and we are looking for a Software Engineer. You will be part of a fast paced team which is responsible for the APIs that Partners and Merchants use to integrate with Affirm, and also power some of our top partners like Amazon and Stripe. What You'll Do · With the support of your team, you will work on tasks that contribute to the team's projects and goals. · You will work collaboratively and proactively with your team and stakeholders, bringing them along for your work and helping to create visibility and dialog regarding the risks and trade-offs related to your work. · You will strike the right balance of speed and quality in your work, ensuring that we hit our business goals while protecting our systems from downtime. · You will contribute to a sense of community on your team by engaging in growth and development activities. What We Look For · You have previous work or internship experience designing, developing and launching backend systems at scale and are experienced using one of Python or Kotlin. · You are familiar with the building blocks of distributed systems, and the technologies like AWS, MySQL and Kubernetes. · You have mastered taking a simple problem or business scenario into a solution that interacts with multiple software components, and executing on it by writing clear, easily understood, well tested and extensible code. · You are comfortable navigating a large code base, debugging others' code, and providing feedback to other engineers through code reviews. · Your experience demonstrates that you take ownership of your growth, proactively seeking feedback from your team, your manager, and your stakeholders. · You have strong verbal and written communication skills that support effect

At Affirm, we exist for the moments that matter—giving people a clear, predictable way to pay over time, with no hidden fees, no surprises, and no tradeoffs on what matters most. Auth Experience owns the customer journeys during authentication, verification, and fraud journeys. You'll work to build the backend orchestration layers that drive our Web and Mobile surfaces. In this role, you will need to gain a deep understanding of the business, product and engineering context, and utilize that context to own and deliver high-availability and low-latency systems that Affirm customers use every day. What You'll Do · You will be responsible for owning and delivering quarterly goals for your team, leading engineers on your team through ambiguity to solve open-ended problems, and ensuring that everyone is supported throughout delivery. · You will support your peers and stakeholders in the product development lifecycle by collaborating with product management, design & analytics by participating in ideation, articulating technical constraints, and partnering on decisions that properly consider risks and trade-offs. · You will proactively identify project, process, technology or business issues, advocate for them, and lead in solving them. · You will support the operations and availability of your team’s artifacts by creating and monitoring metrics, escalating when needed, and supporting “keep the lights on” & on-call efforts. · You will foster a culture of quality and ownership on your team by setting or improving code review and design standards for your team, and advocating for them beyond your team through your writing and tech talks. · You will help develop talent on your team by providing feedback and guidance, and leading by example. What We Look For · You have 4+ years of experience designing, developing and launching backend systems at scale using languages like Python or Kotlin. · You have a track record of developing highly available distributed systems us

At Affirm, we exist for the moments that matter—giving people a clear, predictable way to pay over time, with no hidden fees, no surprises, and no tradeoffs on what matters most. The Growth Platform Engineering team builds the core systems and tools that drive user acquisition, engagement, and lifecycle growth at Affirm. Our platform enables personalized communications, intelligent experimentation, and scalable services that help customers discover and adopt Affirm’s products. We collaborate closely with Product, Data Science, and Experience teams to design APIs, event-driven services, and experimentation frameworks that reach millions of customers across thousands of merchants. This team’s work directly impacts how customers experience Affirm and fuels our long-term growth. We’re looking for a passionate Senior Software Engineer to design and build backend systems that power Affirm’s growth engine. This is a high-impact, cross-functional role that combines technical excellence with strong product intuition. You’ll contribute to scalable, secure, and extensible services that enable Affirm to reach new customers, improve engagement, and expand our product ecosystem. The systems you build will directly influence customer experiences and Affirm’s overall growth trajectory. What you'll do Drive planning and prioritization of projects based on product, technical, and business goals using data-driven decision making. Design and build scalable backend systems, APIs, and data models that power communications, experimentation, and personalization. Partner with Product Managers, Data Scientists, and Analysts to define and execute strategies for customer acquisition and engagement. Establish and uphold engineering best practices to ensure services are secure, observable, and performant at scale. Mentor and support junior engineers, contributing to a culture of learning, collaboration, and technical excellence. What we look for 6+ years of experience as a Software Engineer with