Principal Windows & Active Directory Engineer (L4/SME)
Location: Singapore
Level: Principal Engineer / L4 / SME
Role Overview
We are looking for a highly experienced, hands-on Principal Windows & Active Directory Engineer (L4/SME) to support a large-scale enterprise Windows infrastructure environment.
The environment consists of approximately 2,000 users, including around 1,500 legacy Windows servers/systems running older Windows versions. A key focus of this engagement will be server security, vulnerability remediation, OS hardening and remediation of legacy Windows environments, alongside providing deep technical expertise across Windows Server and Active Directory.
This is a senior hands-on engineering role requiring the ability to independently diagnose complex infrastructure issues, lead remediation activities and provide technical direction across the Windows/AD environment.
Key Responsibilities
- Lead Windows Server security, vulnerability remediation and OS hardening activities across a large enterprise server estate.
- Assess, prioritize and remediate security vulnerabilities across approximately 1,500 legacy Windows servers/systems, including older and end-of-life Windows environments.
- Analyse vulnerability findings and determine appropriate technical remediation, configuration changes, patching, upgrades or mitigating controls.
- Implement and maintain Windows security baselines, OS hardening standards and configuration controls.
- Provide Principal/L4-level engineering expertise for Microsoft Active Directory and Windows Server infrastructure.
- Manage and troubleshoot Active Directory Domain Services (AD DS), Domain Controllers, Group Policy (GPO), DNS and DHCP.
- Perform advanced troubleshooting of AD replication, Kerberos, LDAP/LDAPS, trusts, authentication, authorization and Sites & Services.
- Troubleshoot complex Windows Server and Active Directory production issues and lead root-cause analysis and permanent remediation.
- Perform infrastructure and AD health assessments and identify security, stability and performance risks.
- Support Windows Server upgrades, migrations and modernization of legacy infrastructure.
- Identify dependencies and risks associated with legacy applications and operating systems and recommend appropriate remediation, upgrade or migration approaches.
- Drive patching, security configuration and vulnerability closure activities in collaboration with Cybersecurity and Infrastructure teams.
- Develop and utilize PowerShell automation for administration, vulnerability remediation, hardening, health checks and repetitive infrastructure activities.
- Support server provisioning and infrastructure management within VMware and/or Hyper-V environments.
- Work closely with Cybersecurity, IAM, Network, Application and Infrastructure teams to resolve complex technical and security issues.
- Provide technical guidance to L2/L3 engineers and act as the escalation point for critical Windows/AD issues.
Required Experience & Skills
- 10+ years of hands-on Windows Infrastructure / Active Directory engineering experience.
- Experience operating at Principal Engineer, L4 Engineer, Technical Lead or Windows/AD SME level.
- Deep technical expertise in Windows Server and Microsoft Active Directory.
- Strong experience in server security, vulnerability remediation and Windows OS hardening.
- Proven experience supporting and remediating legacy / end-of-life Windows environments.
- Strong knowledge of AD DS, GPO, DNS, DHCP, Domain Controllers, replication, trusts, Kerberos and LDAP/LDAPS.
- Strong experience with Windows Server 2016/2019/2022 and older Windows environments.
- Experience performing Windows patching, vulnerability remediation, security baseline implementation and configuration hardening.
- Strong PowerShell scripting and automation capabilities.
- Proven ability to troubleshoot complex production infrastructure issues and perform detailed RCA.
- Experience working within large-scale enterprise environments, ideally supporting 1,000+ servers.
- Good understanding of virtualization technologies such as VMware and/or Hyper-V.
- Experience within banking, financial services or other highly regulated enterprise environments would be highly advantageous.
Preferred Profile
We are particularly interested in hands-on Principal/L4 engineers rather than purely architectural profiles. The successful candidate should be comfortable working directly on complex Windows and Active Directory environments and taking ownership of large-scale security hardening, vulnerability remediation and legacy infrastructure modernization initiatives.
50 Raffles Place, #07-01 Singapore Land Tower, Singapore 048623
PERSOL Singapore Pte Ltd • RCB No. 200007268E : EA License No. 01C4394 • EA Registration No. R1113321
