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Senior Systems Engineer (L3) - Network & Infrastructure

Advantage Microsystems

San Jose, CA • $100,000 to $140,000 / yr • 10/1/2026

Job Description

Job Description

Senior Systems Engineer (L3) – Network & Infrastructure

Privately held MSP serving mid-market nonprofits. Not PE-backed.

We're a Northern California MSP with 23 employees, serving clients across several industries, with our growth focused on midsized to large community-based nonprofits: behavioral health providers, child welfare orgs, shelters, and community health centers. The people doing some of the hardest and most overlooked work in the state.

We're not PE-backed and we're not for sale. We've been privately held since 1998 and intend to stay that way. Our goal is to help organizations doing good, not optimize for shareholder value by cutting service, breaking promises, and change-ordering clients to death.

On to the job:

We need someone who's already operated as an L3 or senior engineer and can lead projects, ideally at an MSP. This isn't a service desk role. Our service desk handles day-to-day support and routine escalations. We need someone who can take technical ownership of the complex infrastructure work across our client environments: networking, virtualization, servers, and the problems that land with the most senior engineer in the room.

Clients come to us with legacy on-prem infrastructure and we move them to cloud. Networking is where we need the most depth. The on-prem systems don't disappear overnight, so expect to own server and virtualization environments for at least the next couple of years, and to run the migrations that retire them.

You'd be an important part of a larger team. Our fractional IT directors/vCIOs own the client relationship and roadmap, our technical lead owns architecture and standards across the company, our security specialists handle threat detection and response, and our service desk covers day-to-day support.

You'll also work directly with client leadership. You're the technical voice in those conversations: what the infrastructure can do, what it will cost, what the risk is if it waits. Our vCIOs own the roadmaps and budgets, and they rely on you to make them real. You're not just showing up for the implementation.

Our clients range from about 100 to 1,000 employees, many across multiple sites. They rely on us as an extension of their IT leadership and engineering team, not just another ticket queue.

Six months in, you're leading our most complex projects and helping clients make important technology decisions.

The work:

  • Serve as the final technical escalation point for complex infrastructure issues
  • Lead projects including multi-site network refreshes, SD-WAN/SASE rollouts, firewall and core switch replacements, circuit consolidation, datacenter migrations, and moving on-prem workloads to cloud
  • Own and maintain server and virtualization environments through their remaining life
  • Own the infrastructure standards and reference architectures our team builds against
  • Design solutions alongside our technical lead
  • Support HIPAA and related compliance efforts from the infrastructure side. We support the compliance function, we don't own it
  • Mentor service desk staff and junior engineers

Stack:

Routing and switching, Fortinet/Palo Alto/SonicWall firewalls, SD-WAN/SASE, multi-site WAN and circuit environments, Windows Server, VMware vSphere, hyperconverged infrastructure (VxRail, Nutanix, or similar).

You:

You've spent enough time in infrastructure that you've seen what works, what doesn't, and what tends to break at 2 a.m.

We're looking for 8+ years in IT, 3+ operating at a senior or L3 level. Enterprise networking is where we need the most depth - routing, switching, firewalls, multi-site connectivity. You also need to be solid on Windows Server and VMware or hyperconverged platforms, since you'll be running those environments while they're still in production and planning what replaces them. Healthcare or clinical experience is a plus, especially if you've worked in environments where uptime and change control matter.

MSP experience is strongly preferred. The pace is different, and it helps if you already understand what it's like to move between multiple client environments without losing context.

Strong written communication matters. Certs valued but not required - CCNA/CCNP, advanced Fortinet certifications, VMware VCP, or similar.

The numbers:

  • $100k–$140k base DOE plus bonus
  • Our average employee tenure is 9.5 years
  • We've been work from home since 2004
  • Company-paid health (Blue Shield PPO or Kaiser), dental, vision; subsidized dependents
  • Company-sponsored Life Insurance, short and long-term disability and EAP
  • 401k w/ match, paid certs/exams, mileage, virtual lab
  • 15 days PTO. 20 days PTO at 3yrs. 25 days PTO at 5yrs
  • 9 holidays + your birthday off

This role is remote, with occasional travel to client sites in the San Francisco Bay Area (we cover travel). You'll work Pacific business hours, so candidates in Pacific or Mountain time are preferred.

Some of our clients handle export-controlled data, so this role requires U.S. person status (U.S. citizen, lawful permanent resident, or protected individual such as an asylee or refugee).

We promote from within whenever we can, so this is a rare external search driven by growth.

If you've spent a career making infrastructure work and you'd rather do that for organizations that actually help people than for the next acquisition target quietly gutting its service to hit a number, give us a look.