Senior Backend Engineer, Shopping Agents

Fusion AI Labs

. Own architecture, code, deployments, monitoring, and on-call for systems transacting around the clock .

Posted 11/3/2026full-timeSan Francisco • California • United StatesSeniorWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates expertise in building and operating backend infrastructure systems with a strong focus on correctness and observability, particularly in environments handling real customer payments. Proficient in Python and experienced in deploying AI-first products and LLM-based agents.

Highest-signal resume keywords

Python ProgrammingProduction Systems OwnershipInfrastructure ScalingAI-First Product DevelopmentE-Commerce Background

ATS Keywords

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Hard Skills

Backend Systems DevelopmentInfrastructure ArchitectureObservability ImplementationAdversarial Systems Problem SolvingEmbedding-Based RetrievalLLM Query UnderstandingRerankingCaching

Soft Skills

AdaptabilityProblem-Solving

Industry Keywords

E-CommercePaymentsFraud InfrastructureRisk Infrastructure

Tech Stack

Tools & technologies

Python

About the role

Key responsibilities & impact

Own architecture, code, deployments, monitoring, and on-call for systems transacting around the clock
Build and operate checkout agents using frontier-model computer-use agents for live checkouts at scale
Make checkout-agent failures rare and recovery automatic across changing retailer systems
Scale product ingestion from hundreds of sources to thousands
Build infrastructure that generates, validates, and monitors product ingestion itself
Implement embedding-based retrieval, LLM query understanding, reranking, and caching
Work directly with the CTO

Requirements

What you’ll need

5+ years building backend and infrastructure systems
Strong Python skills
Experience owning production systems end to end, including deploys, databases, observability, and on-call
Ability to solve adversarial systems problems
Strong focus on correctness for systems handling real customer payments
Ability to work without a finished specification in a changing roadmap
Experience building AI-first products or LLM-based agents in production (nice to have)
Working knowledge of classic ML and deep learning, including retrieval and ranking (nice to have)
Background in e-commerce, payments, or fraud and risk infrastructure (nice to have)
Legally authorized to work in the United States
Willing and able to work onsite 3 days a week in San Francisco

Benefits

Comp & perks

Meaningful early-stage equity
Medical, dental, and vision coverage
Other benefits