Staff Software Engineer

Job Description

Senior Principal / Staff Engineer — Watchtower Labs

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In-person only - Bellevue, WA

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U.S. Citizenship required (DoD Clearance preferable)

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How to apply

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Email View email address on ziprecruiter.com with three bullets that prove you can do this. No long intro. No generic claims. Only outcomes with evidence. For example, “Created a new approach to D: enabled capability E that didn’t exist before.”.

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This is not a “backend engineer” role in the usual sense.

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This is a seat for a creator: someone who can take an undefined, high-stakes problem and produce a working system that survives reality: load, edge cases, adversarial conditions, security constraints, and changing requirements.

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If you need a perfect spec, gentle timelines, and a clean handoff chain, do not apply. If you want to build what doesn’t exist yet and you’re wired for hard problems, read on. Instruction for applying below.

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The mission

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We build simulation and autonomy infrastructure that supports critical outcomes for US defense. The work is demanding because the domain is demanding: uncertainty, complexity, speed, and correctness all at once.

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The work

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You will own core systems behind a multi-agent simulation engine:

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• Design primitives: orchestration, state, time, execution models, and scaling strategy
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• Build and run distributed services that must be reliable, observable, and secure
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• Drive performance until it hurts: profiling, contention, memory, throughput, p99s
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• Build infrastructure that behaves under stress, not just in a demo
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• Make calls with incomplete info and be right often enough to move fast
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• Lead by doing: you’ll ship critical pieces yourself and pull others up with you
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The bar

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We’re looking for rare engineering traits:

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• Architect-level judgment: you see failure modes before they happen
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• Relentless ownership: you fix what you touch, and you touch what matters
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• Grit: you don’t get fragile when the system fights back
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• Curiosity: you chase first principles, not vibes
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• Competitive excellence: you care about being great, not merely “done”
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Proven track record of tangibly contributing to complex systems.

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What you should bring

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• Deep experience building real systems in production (distributed, performance-sensitive, mission-critical)
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• Comfort working across C#/.NET Core, Linux, Python (or equivalent mastery + fast learning)
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• Strong mental model of systems: concurrency, networking, data integrity, deploy/release, observability
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• Ability to thrive in-person with a high-output team and high standards
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What you will get

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• The kind of problems that force you to level up
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• A team that values builders and moves fast without lying to itself
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• Work with real consequences and real pride when it ships
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