Senior Backend Engineer

About Antithesis

We've been quietly reinventing how the world thinks about software reliability, and we're just getting started! At Antithesis, we start at the foundations - we run entire software systems inside a deterministic simulation and break them in every way imaginable. Every issue then comes with a perfect reproduction, so you can identify root causes fast instead of spending days trying to recreate what went wrong.

The rise of AI-generated code has made this work more urgent than ever. Agents can write code faster than any human, but speed doesn't matter much when the output is buggy, stuck in review, or slipping through undetected. The verification bottleneck is real, it's growing, and solving it is one of the most consequential problems in software right now. That's what you'd be working on.

We're well-funded and deeply technical, the kind of place where the hardest problems get the most attention and the best ideas win regardless of who has them. If you want to do work that actually moves the needle on how reliable software can be, keep reading.

About the Role

The Platform team is the engine room of Antithesis - we own the infrastructure, services, and tools that are at the core of the product. As a Senior Backend Engineer here, you won't be maintaining someone else's abstractions. You'll be designing them from scratch, owning them end-to-end, across the full stack: from raw binary formats and block compaction all the way up to the external APIs our customers depend on. Correctness and performance aren't nice-to-haves here - they're the job.

If you get unreasonably excited about systems design, performance, storage efficiency, clean API contracts, and finding the bottleneck nobody else noticed, we'd love to talk.

What You'll Do

• Design, build, and operate core platform systems - including backend infrastructure, data processing pipelines, storage layers, and the scalable APIs, integrations, and interfaces that power internal and external consumers.
• Contribute to Pangolin, our purpose-built database designed from the ground up to meet the unique demands of our platform.
• Build and evolve foundational platform primitives such as data access layers, authorization frameworks, and service orchestration.
• Own reliability end-to-end - from system design and capacity planning to incident response, with a sustainable on-call rotation shared across the team.
• Identify and resolve performance bottlenecks across the stack; mentor engineers; contribute to long-term technical strategy.

What We're Looking For

• 5+ years of software engineering experience. Rust is a strong preference, but exceptional systems engineers from other backgrounds are welcome.
• Experience building APIs, services, storage engines, query engines, or data-intensive backend systems.
• Deep understanding of distributed systems: consistency, fault tolerance, replication, observability.
• Hands-on experience designing and shipping APIs with attention to correctness and contract stability.
• Strong fundamentals - you care about correctness, test coverage, and well-designed abstractions.
• Bonus: query planning/optimization experience, multi-tenant platform or authz background, C/C++ familiarity, or open-source contributions.

About Our Team

Our team has backgrounds spanning CS degrees, philosophy, mathematics, and everything in between - or nothing formal at all. What everyone shares is a high bar for engineering quality, regardless of title. We work in-person because it's how we build trust and tackle hard problems together.

Location: This position is in office in Vienna, VA.