Senior / Staff Software Engineer (AI Agents)

Actively; San Francisco (CA); On-site; USD 180,000 - 220,000; Full time

Job summary

Actively AI in San Francisco is seeking a Senior/Staff Backend Engineer to architect and build large-scale systems powering our GTM AI agents. You’ll design scalable, event-driven infrastructure, integrate with LLMs, orchestrate complex workflows, and ensure reliable actions across systems with humans in the loop.

As a strong backend thinker, you’ll model stateful agents, implement robust data contracts, and push for observability and fault tolerance.

Qualifications

• Experience building large-scale backend systems with distributed components.
• Strong Python skills, with a focus on concurrency and performance.
• Ability to design reliable, observable, fault-tolerant services.

Responsibilities

• Design and build agents that power Actively’s platform at massive scale.
• Develop orchestration and workflow primitives for agent/human collaboration.
• Ensure reliability with clear state machines and robust data contracts.
• Evolve agent design as capabilities and data volumes grow.

Skills

Backend engineering

Python expertise

Distributed systems

Event-driven design

Architecture thinking

Product-minded

Collaboration

Tools

Kafka

Temporal

LLM integration

Relational/NoSQL DBs

In-memory stores

Job description

About Actively AI

Actively AI is defining a new category: Intelligence-Led Revenue.

Revenue organizations have always been bottlenecked on human capacity. Reps triage which accounts get attention. Context disappears at every handoff. On any given day, the vast majority of accounts have exactly zero people thinking about them.

Actively addresses this at the structural level. Our platform deploys Per-Account AgentsTM across our customers’ TAM, working 24/7 to research, identify opportunities, and advance next steps without being asked. Leading enterprises including Ramp, Ironclad, and Samsara are already making this shift.

Our co-founders are former Stanford AI researchers, and the team comes from Harvard, CMU, Berkeley, Brex, Scale AI, and Google. We've raised $68M from TCV, First Harmonic, Bain Capital Ventures, First Round Capital, and more.

About the Role

We’re looking for a Senior/Staff Backend Engineer to architect and build large scale systems that power Actively’s GTM AI agents. These agents continuously reason over real-time customer and external data, generate next-best actions, and execute them reliably across systems with humans in the loop.

In this role, you’ll design the scalable, event-driven, and fault-tolerant infrastructure that makes this intelligence possible — integrating with LLMs, orchestrating complex workflows, and ensuring every action happens with high reliability. This is a foundational role, shaping how production-grade agents operate at enterprise scale.

What You’ll Do

• Design and build the agents that power Actively’s platform. Model complex customer and business workflows into clear, reliable agent logic that reasons over streaming data, maintaining state, decides what to do next, and acts consistently across systems — continuously and at massive scale.
• Develop orchestration and workflow primitives for agent and human collaboration. Translate nuanced, long-running real-world scenarios — multi-step workflows, customer-specific rules, and human-in-the-loop actions — into well-structured agent behaviors that are predictable, maintainable, and easy to extend.
• Ensure reliability through good modeling. Design agents with clear state transitions, strong data contracts, and explicit guarantees — embedding observability and fault tolerance into their design so they behave correctly over millions of events and long‑held sessions.
• Continuously evolve agent design. Simplify complex behavior through better abstractions, documentation, and testing — ensuring agents remain reliable and comprehensible as capabilities, data volume, and concurrency grow.

Who You Are

• Experienced systems builder. You’ve designed and operated large-scale, event-driven backend systems — modeling complex, long‑lived workflows into clear, maintainable, and reliable software.
• Strong backend engineer. Deep Python expertise and solid fundamentals in concurrency, transactions, and performance tuning.
• Architectural thinker. You reason about trade‑offs between consistency, latency, fault‑tolerance, and cost — building for correctness and adaptability.
• Product-minded. You care about usability, developer experience, and how system design translates into real customer value.
• Fluent in modern infrastructure. Familiar with streaming and workflow technologies (Kafka, Pub/Sub, Temporal‑like), and data stores across relational, in‑memory, and vector paradigms.
• Collaborative and pragmatic. You value iteration, clear communication, and helping others move faster without sacrificing quality.
• Curious about AI systems. You’re excited by how LLMs, retrieval systems, and agents can transform enterprise software — and you want to build the infrastructure that makes it real.

Nice to Haves

• Built or contributed to LLM‑powered or agent‑driven systems — such as real‑time inference pipelines, context and retrieval systems, or human‑in‑the‑loop orchestration.
• Experience scaling mission‑critical systems with high reliability requirements (payments, messaging, logistics, orchestration).
• Comfort working in fast‑moving, high‑ambiguity environments where you balance big vision with tactical delivery.

Why Join

It’s not often that you can get in on the ground floor of a well‑funded startup that’s scaling very fast. That means that instead of following a playbook, you’ll be writing it. Every single day you will be challenged to identify how we can scale and execute on it. You’ll learn what works when you succeed and what doesn’t when you fail. You'll also be in the trenches with an incredibly high caliber, low‑ego group of people that are obsessed with building something great.

Benefits

• Competitive Early‑Stage Equity
• Health, Dental, Vision Coverage
• Unlimited PTO + Recharge Days
• Catered Lunch on Tuesday & Friday w/ Dinners every day!
• Fully Stocked Kitchen
• Cutting‑Edge Tech & Tools
• Annual Off‑sites & Monthly Events
• Commuter Benefits
• Cozy Office in SF

The base salary range for this full‑time position based in San Francisco is: $180,000 - $220,000.

Note on Pay Transparency:

Actively AI provides an estimate of the compensation for roles that may be hired as required by state regulations. Compensation may vary based on (a) location, as Actively AI factors in specific location when benchmarking compensation for most roles; (b) individual candidate skills and qualifications; and (c) individual candidate experience. Additionally, Actively AI leverages current market data to determine compensation, so posted compensation figures are subject to change as new market data becomes available. The salary, other compensation, and benefits information is accurate as of the date of this posting.

Actively.ai reserves the right to modify this information at any time, subject to applicable law.

Actively AI is committed to equal treatment and opportunity in all aspects of recruitment, selection, and employment without regard to gender, race, religion, national origin, ethnicity, disability, gender identity/expression, sexual orientation, veteran or military status, or any other category protected under the law. Actively AI is an equal opportunity employer; committed to a community of inclusion, and an environment free from discrimination, harassment, and retaliation.

Why Join

At Actively, you write playbooks rather than follow them. You own outcomes, not just tasks, and see directly how your work changes what customers can do — across a product and go‑to‑market motion that is scaling fast. The team is high‑caliber and low‑ego: people who work from first principles, move with urgency, and care deeply about building something that drives real value. If that's the kind of challenge you're looking for, Actively is the right place.

Benefits

• Competitive Early‑Stage Equity
• Health, Dental, Vision Coverage
• Unlimited PTO + Recharge Days
• Catered Lunch on Tuesday & Friday, Dinners every day!
• Fully Stocked Kitchen
• Cutting‑Edge Tech & Tools
• Annual Off‑sites & Monthly Events
• Commuter Benefits
• Cozy Office in NYC