Senior SharePoint Developer (SPFx / .NET)

We are looking for two Senior SharePoint Developers to take over and further develop enterprise applications built on SharePoint on-premises for a European public institution in Warsaw. This role suits a mature, experienced engineer who is comfortable working with an existing codebase and working directly with business stakeholders. About the Project: The client runs a set of line-of-business applications built on SharePoint Server (2019 / Subscription Edition), with custom SPFx components and .NET Web APIs behind them.

The applications were built by a third-party vendor, and the new team will take over the codebase from them. There is a knowledge transfer period in November 2026, overlapping the current contractor's last sprints. You will join a Scrum team that works in Azure DevOps, alongside business owners, analysts and testers.

The assignment is long term.

Develop and maintain SharePoint on-premises solutions using SPFx, React, TypeScript and PnPjs; Build and maintain custom Web APIs in .NET/C# hosted on IIS, with SQL Server; Take over an existing third-party codebase through code review, refactoring, technical debt management and regression testing; Integrate applications with identity and external systems (EU Login, SAML, Entra ID, REST APIs, notifications, document management); Optimize the performance, security and quality of list-based SharePoint solutions; Translate requirements into technical design, using UML where needed; Estimate effort, take