Senior Windows Infrastructure Design Engineer (L3/L3.5)

About the Role

We are seeking an experienced Windows Infrastructure Design Engineer to join our Infrastructure Engineering team. This role is responsible for the architecture, engineering, governance and highest-level technical support (L3/L3.5) of the organisation's Windows Server, Active Directory and identity infrastructure across datacentre, cloud and hybrid environments.

The successful candidate will be a senior technical authority for Microsoft server and identity technologies, providing design leadership, operational governance and engineering expertise. The role combines deep Windows and Active Directory knowledge with experience of Privileged Access Management (PAM), automation and modern infrastructure management practices.

The engineer will play a key role in modernising infrastructure services, improving security posture, driving automation and supporting large-scale transformation initiatives across the enterprise estate.

Key Responsibilities

• Design, implement and maintain enterprise Windows Server infrastructure and associated platform services.

• Own the architecture and governance of Active Directory Domain Services (AD DS), including domain, forest, trust and replication design.

• Design and support Microsoft DNS services hosted on domain controllers and integrated with Active Directory.

• Define and maintain standards, reference architectures and operational processes for Windows and identity services.

• Act as the L3/L3.5 escalation point for complex Windows, Active Directory and authentication-related issues.

• Design and support enterprise identity and access management solutions, including integration with PAM platforms.

• Develop and implement security hardening standards in line with industry best practices.

• Collaborate with security, networking, cloud and application teams to deliver resilient and secure infrastructure services.

• Design and implement automation solutions using scripting, Infrastructure as Code and API-driven management.

• Leverage AI-assisted tooling to improve operational efficiency, troubleshooting, reporting and knowledge management.

• Provide technical leadership for infrastructure transformation, cloud migration and service modernisation programmes.

Required Experience

• Extensive experience designing and supporting Microsoft Windows Server environments.

• Strong expertise in Active Directory Domain Services, including:

• Forest and domain design

• Group Policy

• Sites and services

• DNS integration

• Trust relationships

• Replication

• Authentication services

• Strong understanding of Microsoft DNS, DHCP and certificate services.

• Experience supporting hybrid identity environments incorporating Active Directory and Microsoft Entra ID.

• Experience with Privileged Access Management (PAM) solutions and privileged account controls.

• Strong understanding of authentication technologies including Kerberos, LDAP, NTLM and modern identity protocols.

• Experience with Windows security hardening and vulnerability remediation.

• Experience with PowerShell automation and configuration management.

• Strong troubleshooting and root-cause analysis capability across complex enterprise environments.

• Experience supporting highly available