Senior Systems Engineer

We are looking for an experienced Senior Systems Engineer with deep Windows Server expertise to join our infrastructure team. This is a hands-on technical role with real variety - spanning day-to-day operations, incident resolution, and proactive improvements across a complex, multi-tenant AWS environment.

You’ll take ownership of Windows infrastructure work at all levels of complexity, working closely with senior engineers on challenging problems and contributing directly to the reliability and growth of the platform. As a senior member of the team, you’ll also be expected to provide technical guidance, contribute to architectural decisions, and help drive improvements across the platform.

Key Responsibilities

Windows Server & Active Directory

• Administer and maintain Windows Server environments (2016/2019/2022) across multiple customer tenants.

• Design, deploy, and troubleshoot Group Policy Objects (GPOs) to effectively secure customer-facing environments, including AppLocker policies to restrict access to shell executables.

• Manage NTFS and share permissions across multi-tenant file server environments.

• Administer and support our RDS/TSplus environment during migration to new platforms.

• Mentor and develop colleagues across the team, sharing knowledge and building infrastructure capability.

AWS Infrastructure

• Operate and support a fleet of over 600 Windows and Linux EC2 instances using monitoring and patching tooling.

• Support customers during migration to and day-to-day use of WorkSpaces Applications (AppStream 2.0).

• Contribute to the design and delivery of AWS end user computing solutions, including WorkSpaces Applications fleet management, image lifecycle, and profile strategies.

• Troubleshoot and manage AWS networking infrastructure including VPC routing, Security Groups, and related services.

• Work across multi-region, multi-account AWS environments with a clear understanding of tenancy boundaries.

• Contribute to internal platform projects spanning routine maintenance, capacity expansion, and infrastructure upgrades.

• Support the Technical Project Manager in the planning and delivery of infrastructure projects.

Identity & Access

• Administer Okta: users, application assignments, and MFA configuration.

• Troubleshoot federated identity issues across Active Directory and Okta.

Security & Compliance

• Maintain security hardening standards across Windows Server and Linux environments.

• Respond to and document security incidents, including root cause analysis and follow-up remediation.

• Own and maintain robust backup and disaster recovery processes to ensure business continuity across the platform.

Monitoring & Troubleshooting

• Monitor and resolve infrastructure alerts using Zabbix and bespoke internal tooling, ensuring the hosting platform operates at optimal performance levels.

• Act as 3rd/4th line escalation for complex client infrastructure issues, providing expert diagnosis and resolution.

• Diagnose and resolve complex issues across networking, DNS, authentication, and application layers.

• Produce clear incident documentation, root cause analyses, and post-incident reports.

• Extensive hands-on Windows Server administration in a production environment.

• Strong Group Policy experience: creating, troubleshooting, and documenting GPOs in complex Active Directory environments.

• Solid Active Directory fundamentals: OU structure, group management, delegation, and policy inheritance.

• Experience with RDS or similar remote desktop solutions, including multi-session management and profile handling.

• NTFS and share permission management, including inheritance, auditing, and remediation.

• Comfortable working in AWS at an operational level: EC2, VPC, IAM, S3, Route 53.

• Networking fundamentals: VPN configuration, DNS, routing, and firewall rules.

• Strong, methodical troubleshooting approach - able to isolate issues systematically and document findings clearly.

• Experience working in a Managed Service Provider or multi-tenant environment.

• Holds a current AWS certification (Associate level or above) or is ready to sit the exam.

• Demonstrable interest in AWS end-user computing - WorkSpaces Applications, AppStream 2.0, or related services.

Desirable Skills

• Hands-on experience with WorkSpaces Applications (AppStream 2.0) fleet and image management.

• Okta administration experience.

• Exposure to SAP Business One environments.

• Linux fundamentals (SLES, Ubuntu) - sufficient to navigate and perform standard administration tasks.

• Familiarity with Zabbix or CloudWatch monitoring.

• PowerShell scripting - able to write and maintain scripts for administration and automation tasks.

Personal Attributes

• Takes ownership and follows through - doesn’t wait to be told twice.

• Comfortable with ambiguity; able to investigate and resolve issues without a full brief.

• Clear and direct communicator - written and verbal.

• Methodical under pressure; documents as they go.

• Proactively surfaces risks and blockers rather than hoping they resolve themselves.

• Works well independently in a remote-first team., * Have you already achieved an AWS certification, or do you plan to pursue one in the next few months?
• Briefly describe your experience creating and managing Group Policy Objects (GPOs).
• Briefly describe your experience working with remote desktop/session host environments.
• Briefly describe your experience configuring and managing VPNs (e.g. site-to-site, client VPN).

• Competitive salary, dependent on experience.

• Genuine flexibility over how and when you work, with scope to build in out-of-hours or weekend cover in a way that suits you as the team grows.

• Exposure to a broad and genuinely complex technical environment.

• Opportunity to grow into more senior or specialised roles as the team scales.

• Direct collaboration with senior engineers - no layers of bureaucracy.

Ascarii Ltd · August 2026

Pay: £30,000.00-£50,000.00 per year

Benefits:

• Casual dress
• Company pension
• Employee discount
• Free parking
• Health & wellbeing programme
• On-site parking
• Work from home

Ascarii are an SAP Gold Partner and AWS Partner with over 14 years of experience delivering SAP Business One cloud hosting and consultancy to clients and partners worldwide. As we continue to grow our global customer base and expand our SAP on AWS offering, we’re looking for a Senior Systems Engineer to join the team and help us maintain the high standard of support our customers expect.

Our Operations Technical Team is based in Sedgefield, UK, with additional team members working remotely. We believe in getting the balance right - we expect everyone to own their work and take pride in what they deliver, but you’ll never be left to struggle alone. The team is genuinely collaborative, and whether you’re dealing with a complex incident or working through something unfamiliar, there’s always someone to think it through with.