Senior Software Engineer; Full Stack

We're solving a multi-billion dollar problem: AML/KYC compliance is slow, expensive, and drowning in false positives. Castellum.

AI is an all-in-one AI agents and screening platform that cuts false-positive alerts by up to 94% compared to legacy providers, and we're growing fast as new customers come on board.

You'll join a growing engineering team and own meaningful projects end to end: data pipelines, our Go API layer, AI agents, and the platform our customers rely on every day. This is a high-agency role for someone who wants to take an ambiguous problem, decide how to solve it, and ship it.

• ~1 hour/day in meetings. Standup, sprint planning, retro. We keep it light.

• The rest of the day is building. Feature work and bug fixes, going from architecture decision to shipped code. You'll use AI/LLMs as a force multiplier but you own the tradeoffs and QA your own changes.

• Real ownership. You take a project and run with it. You help decide what's in scope, what's out, and where it's okay to cut a corner.

• On-call. A one-week rotation shared across the team, mostly during ET business hours.

We run a modern stack (Docker, Kubernetes, and similar tooling), and you have a dedicated Dev Ops engineer handling the heavy infrastructure lifting so you can stay focused on building.

• API layer: Go, gRPC, protobufs

• Agents & ETL / data pipelines: Python

• Frontend: Type Script + React

• Data: PostgreSQL, Elasticsearch

Our strongest engineers share a few traits:

• High agency and urgency. They move quickly, take ownership, and understand that getting things done matters. They've worked on small teams that had to ship to survive.

• Architecture to code. They can write an architecture doc, break the work into manageable chunks, and then build it.

• Good judgment, including with AI. They use AI tools well without leaning on them blindly. They catch when the model makes the wrong tradeoff and they ship code they understand and stand behind.

• Clear communicators. They communicate well within engineering (and ideally with customers), understand customer requirements, and will push back on a decision but can disagree and commit.

Required

• Strong professional experience building web applications, APIs, and back-end systems (5+ years)

• Python or Go experience

• Plus strong experience in Type Script . You don't need all three on day one; we expect you to ramp on the one you know least

• Experience with PostgreSQL or similar relational databases technology

• Clear written and verbal communication

• Experience getting real value out of AI developer tools

• Prior startup or small, fast-moving team experience

Nice to have

• Experience with Elasticsearch, gRPC/protobufs

• Experience building AI agents

• Experience with containerization and distributed systems

• Fully remote, US-based, working Eastern hours.

• We work hard but we don't burn out. Expect ~45–50 hour weeks. Life happens, and there's real flexibility when it does.

• We like each other. We have as much fun as we can while we work, and it's genuinely exciting to watch the business take off.

We move fast and we don't believe in endless interview loops. Most candidates can move at their own pace, as quickly as four days. Every stage is designed to be a real conversation.

• Intro Call: Meet with our CTO to talk through the role.

• Architecture Interview: We'll take a larger problem and break it down together on a virtual whiteboard. We're looking at how you structure a solution and reason about the pieces, not whether you memorized anything.

• Coding Interview: Solve a problem and walk us through your thinking. We care more about how you approach it than about a perfect answer.

• Final Round: Meet…