Senior Staff Software Engineer - Optimization

About The Role Shopify’s Optimization group builds the systems that help Shopify and our merchants make better decisions, launch faster, and learn from real behavior. The group spans Experiments Platform, Rollouts, and SimGym: three independent systems with deep shared problems in experimentation, targeting, metric reliability, analysis workflows, AI simulation, and decision velocity. Experiments Platform powers A/B testing across Shopify. Rollouts give merchants control over how storefront changes go live, from scheduled releases to statistically rigorous A/B tests. SimGym uses AI agents, browser automation, and multimodal models to simulate buyer behavior before merchants launch changes to real traffic. We are looking for a Senior Staff Engineer to be the senior technical leader across this area. This is a hands-on role for someone who can move between strategy and code: defining architecture, writing critical-path systems, mentoring Staff and Senior engineers, unblocking multi-team dependencies, and shaping how Shopify measures impact. The long-term vision is a closed optimization loop: SimGym simulates storefront changes, AI agents propose or implement improvements, Rollouts tests them with real traffic, and live experiment outcomes feed back into SimGym to improve simulation quality. You will help shape and drive that system. What You'll Do Set and drive technical direction across Experiments Platform, Rollouts, and SimGym. Own multiple high-value technical problems at once, ramping quickly across unfamiliar domains and driving timely results. Write, review, and guide critical-path code for systems where correctness, reliability, performance, and operability matter. Design scalable architectures for experimentation, rollout orchestration, AI simulation, assignment, exposure tracking, metric computation, and analysis workflows. Carry learnings between internal and merchant-facing experimentation systems, especially around assignment, targeting, statistical rigor, and data correctness. Help build the path toward a closed optimization loop across SimGym, Rollouts, and merchant-facing recommendations. Navigate ambiguity across engineering, product, data, research, and partner teams, turning broad goals into concrete technical plans. Model accountability for the systems you build and oversee; the hardest technical questions in the area should be able to escalate to you. Simplify systems by removing unnecessary abstraction, legacy complexity, and fragile patterns. Mentor and sponsor C7, C6, and intermediate engineers, raising the bar for technical judgment, code quality, and decision-making. Build strong relationships across Shopify teams including Checkout, Online Store, Growth, Payments, Markets, Shop, and merchant-facing product surfaces. Set the pace for the area by combining urgency with strong judgment. What You'll Need Senior Staff-level engineering experience, with a track record of setting technical strategy across multiple teams, systems, or product areas. Deep systems expertise, including experience building and operating large-scale distributed systems. Strong domain experience in experimentation platforms, statistical analysis systems, data-intensive products, optimization systems, AI simulation, or related infrastructure. Strong judgment around data correctness, metric reliability, exposure tracking, assignment systems, and the ways experimentation platforms can mislead users when implemented poorly. Broad technical range across backend services, data pipelines, frontend systems, and operational infrastructure. Ability to make architecture decisions across consistency, availability, performance, maintainability, and delivery speed. Experience leading complex migrations, platform evolutions, or multi-team technical programs. Operational maturity: you build systems that are easy to understand, debug, operate, and recover. Strong written and verbal communication with engineers, product leaders, data scientists, executives, and partner teams. A high bar for craft: code that is understandable, maintainable, fast where it matters, and built with the important details in mind. Nice To Have Experience with A/B testing infrastructure, sequential testing, CUPED, sample ratio mismatch detection, multi-armed bandits, or metric computation platforms. Experience with merchant-facing launch systems, rollout orchestration, traffic assignment, or feature flag infrastructure. Experience with AI agents, LLM/VLM systems, browser automation, simulation frameworks, model evaluation, or AI-assisted analysis. Experience with Ruby/Rails, TypeScript/React, Python, SQL, Rust, BigQuery, ClickHouse, Kafka, Flink, Kubernetes, GCP, Redis, MySQL, or edge computing. Experience working across internal platform teams and user-facing product teams. How We Work Shopify moves fast, and the Optimization group sits in the middle of ambiguous, high-leverage work. We value people who are comfortable being uncomfortable, who seek the truth directly, and who can turn uncertainty into forward motion. You should be excited to: Treat project requirements as the floor, not the ceiling. Use AI tools reflexively as part of your daily workflow. Prototype and experiment several moves ahead. Challenge orthodox approaches when they are not the best answer. Bring strong opinions, change your mind when the evidence changes, and help others do the same. Be resilient and resourceful when the work is messy. Care deeply about making commerce better for everyone. Inspire the area through example, not just direction. Why This Role This is a high-leverage role at the center of how Shopify and its merchants learn, launch, and optimize. Your work will shape systems used for internal experimentation, merchant-facing rollout control, AI-powered buyer simulation, and the feedback loops that connect them. The breadth is the point. You will work across statistical computing, distributed systems, real-time data processing, product engineering, and applied AI. You will not just optimize an existing system; you will help define the operating model and architecture for Shopify’s next generation of optimization systems. This role may require occasional on-call work. Shopify’s hiring process moves quickly, and candidates should be prepared for a technical interview loop that includes pair programming using their own IDE.