Principal Full Stack Engineer, B2B eCommerce

Fusion Worldwide•Boston, MA

1d•Hybrid

About The Position

Fusion Worldwide is hiring a Principal Full Stack Engineer to serve as a senior technical owner of its B2B eCommerce platform. The platform includes fusionww.com, GraphQL and REST APIs, an internal admin portal, and the event pipeline. The engineer will design and deliver customer-facing and internal commerce features end to end, operate services on Azure, and build AI agents for sales and operations teams. The platform serves business buyers, including OEMs, CMs, and ODMs. Palantir Foundry provides data for customer intelligence and sales workflows; this role consumes Foundry data through its APIs and SDKs and partners with the data team, rather than building within Foundry. The team is AI-first: Claude Code is part of daily development, AI code review is required for every pull request, and Claude-powered agents run in production. The expected allocation is approximately 80% application development, 10% AI agents and LLM features, and 10% infrastructure and DevOps. This is a full-time, hands-on individual contributor role reporting to the Team Lead, eCommerce, based in Boston, Massachusetts, with a hybrid workplace arrangement. The successful candidate will bring 10 or more years of professional software engineering experience, including substantial work with B2B eCommerce or other commercial systems. They will have expert relational database skills, experience with Azure or an equivalent cloud and Terraform, and practical experience building with LLMs or agents and using AI coding assistants. They will own code quality and testing, production issue resolution, architecture decisions and documentation, and collaboration with business stakeholders.

Requirements

10+ years of professional software engineering experience, including significant time building or running B2B eCommerce or other commercial systems involving areas such as catalog, pricing, quoting, orders, checkout, or ERP integration.
Expert-level relational database skills, including schema design, query tuning, and concurrency; SQL Server is preferred.
Hands-on experience with Azure or an equivalent cloud, including containerized services and infrastructure as code with Terraform.
Experience building with LLMs or agents.
Daily practical use of AI coding assistants such as Claude Code, with sound judgment about verifying their output.
Experience with Git and GitHub, GitHub Actions, Jira, and Agile/Kanban delivery.
Clear written communication and ability to explain tradeoffs to business stakeholders.

Nice To Haves

Distribution or marketplace commerce experience, especially involving complex pricing, quoting, or inventory.
Experience with Algolia, HubSpot, or event-driven architecture.
Electronic components or supply chain domain knowledge.

Responsibilities

Design and deliver features across the customer site, GraphQL backend, and REST services.
Own core commerce flows, including search and discovery, catalog and pricing display, quoting and RFQ, cart and checkout, and order status.
Build internal admin portal tools for sales, marketing, operations, and compliance.
Work across Azure SQL/SQL Server, Redis, Algolia, and event-driven processing with Celery and Azure Service Bus.
Integrate with HubSpot, Amplitude, Contentful, and Fusion's ERP through its API layer.
Consume Palantir Foundry data through Ontology objects, OSDK, and APIs to support customer intelligence and sales workflows, partnering with the data team on contracts and requirements.
Build and improve production agents and LLM features using the Claude API, Claude Agent SDK, and Model Context Protocol (MCP).
Manage AI feature cost, token usage, and output quality, and implement evaluations and guardrails.
Use Claude Code as a primary development tool and apply human judgment to every merge.
Operate and extend Azure services, including Container Apps and Jobs, Azure SQL, Front Door and WAF, Key Vault, Service Bus, API Management, Application Insights, and Log Analytics.
Manage infrastructure as code with Terraform and CI/CD with GitHub Actions and Azure Container Registry across development, test, pre-release, and production environments, including an active/active second region.
Improve observability and alerting, and troubleshoot production issues by tracing real data.
Apply secure-by-default practices, including Key Vault secrets, least privilege, safe error handling, and dependency hygiene.
Write well-tested code at every layer and keep it passing in CI.
Test and verify owned work against requirements before release.
Serve as the hands-on technical expert for the eCommerce application and development team.
Triage and resolve user-reported issues and fix bugs across the customer site, admin portal, and APIs.
Make and document architecture decisions, favoring the existing platform over new parallel infrastructure.
Partner with business stakeholders to assess feasibility and shape requirements.
Document findings so future engineers and AI sessions can use them.