Model Systems Engineer

  • Location: Remote
  • Department: Platform
  • Employment Type: Full-time

What’s in it for you?

Pax is an executive assistant for individuals and a chief of staff to organizations. Every judgment it makes runs through a reasoning layer that has to hold quality steady while staying fast and affordable. You would own that layer.

Routing decides which reasoning goes where, at what level of effort, with what fallback when something upstream fails. Get it right and the product feels immediate. Get it wrong and customers feel it before anyone else does. The quality numbers this layer produces are the numbers the rest of the company plans against.

About the team and the opportunity

Paciva is token optimized by design. The platform sends only what is needed to reason, which means quality, speed, and cost all move together when you change how routing works. Few engineering roles put that much of a product’s economics in one person’s hands.

This is a first hire for the domain. You would take a working system and make it something a company can stand on, and you would set how good it gets.

What the role covers

You own reasoning routing and the evaluation that keeps it honest. That means deciding which work gets handled at which level of effort, measuring output against reference results, and adjusting when quality drifts. You own provider health, failover behavior, and the calibration cycle that keeps accuracy measurements current. Cost and latency are yours to defend.

What you will work on

  • Own routing across quality tiers and levels of effort
  • Build and maintain evaluation runs that catch drift before customers do
  • Tune context so the platform spends the fewest tokens that still produce the right answer
  • Add and retire models as the field moves, with a documented process rather than guesswork
  • Set up failover so an upstream outage never becomes a customer outage
  • Publish the quality metrics the rest of the company plans against
  • Work with product on which capabilities need frontier reasoning and which do not

What we need from you

  • 5+ years building production systems, with at least one year on LLM infrastructure
  • Real experience with evaluation, and the discipline to trust the numbers
  • Comfort running open models locally, including quantization and hardware limits
  • Strong instincts about cost and latency tradeoffs under load
  • Ability to explain a routing decision to an engineer and to a customer
  • Bias toward measurement over opinion, and toward simple designs that hold up

Working at Paciva

About Paciva

Paciva is an early stage company with people in Miami, Florida and Austin, Texas. The team works fully remote. Pax is an executive assistant for individuals and a chief of staff to organizations. It connects to the services you already use and does real work end to end, rather than reporting back on what needs doing.

The company is founder led and privately held. Every role we post is a first hire for its domain, which means you set the standard rather than inherit one, and you work with the founders directly rather than through layers.

Compensation and benefits

Compensation is set by role scope, experience, skills, location, market data, and internal equity. Every role carries meaningful equity, because the person who builds a domain from nothing should own part of what they build. For sales roles, compensation combines base salary with variable incentive pay, and the target is stated as on target earnings.

We cover pay and benefits in full in the first conversation, before you spend time on a process. Ask early and we will answer.

Remote work and travel

Every role here is remote. Paciva has people in Miami and Austin, and the team works across time zones. That puts weight on clear written communication, ownership, practical collaboration, and dependable follow through. Most roles include occasional travel for team meetings, customer sessions, company events, or off sites.

How we hire

We read every application. If your experience does not match the list above but you have done work that shows you can do this job, put that at the top.

The process is short and the founders run it. You will spend time on a real problem from the role rather than a hypothetical, and you will meet the people you would work with every day, because there are not many of us. We tell you where you stand at each step and we do not leave anyone waiting.

You are welcome to use AI tools when you apply. We build them. What we want to see is your judgment, so tell us where you used a tool and what you changed about its output.

Accommodations and applicant privacy

If you need a reasonable accommodation to take part in any stage of this process, tell us. You do not need to share medical detail. We will work out what lets you participate fully.

For how we handle the information you send us when you apply, see our applicant privacy notice at https://trust.paciva.ai/ 

Recruiting scam notice

Paciva recruiters only contact candidates from paciva.ai email addresses. We will never ask for money, fees, or banking information at any point before your first day. If a message looks off, do not click anything in it. Come back to paciva.ai and check the open roles here.

Equal opportunity

Paciva is an equal opportunity employer. We make employment decisions based on qualifications, merit, business needs, and role fit. We do not discriminate based on race, color, religion, sex, sexual orientation, gender identity or expression, national origin, age, disability, veteran status, genetic information, marital status, pregnancy, caregiver status, or any other status protected by applicable law.