Principal AI Engineer

About Apollo.io

Apollo.io is the leading go-to-market solution for revenue teams trusted by over 500000 companies and millions of users globally from rapidly growing startups to some of the world's largest enterprises. Our platform helps sales and marketing teams prospect smarter automate workflows and close more deals all within a unified AI-native platform.

Backed by world-class investors including Sequoia and Bain Capital and recently valued at $1.6B following our Series D Apollo is one of the fastest-growing SaaS companies in the world.

Why This Role Matters

We are entering a new phase of AI-native growth and are looking for a Principal AI Engineer to lead the design and deployment of cutting-edge agentic systems AI assistants and LLM-powered features. This role is pivotal to Apollo’s AI roadmap owning the architecture and productionization of intelligent systems that power the workflows of thousands of GTM teams globally.

You’ll be a technical thought leader on the AI Engineering team and work alongside product backend and platform leaders to drive forward Apollo’s competitive edge in applied AI.

What You'll Own & Deliver

End-to-End Agentic Systems

• Autonomous AI Agents : Architect and lead the development of multi-agent systems capable of long-horizon planning reasoning and API orchestration.

• Workflow Automation : Build reusable agentic components that integrate deeply into sales and marketing processes.

• LLM Platformization : Own and evolve our in-house platform for scalable low-latency and cost-efficient LLM and agent deployments.

AI Assistants and Search

• Conversational AI & UI : Lead design of interfaces powered by natural language understanding and retrieval-augmented generation (RAG).

• Semantic & Personalized Search : Build embedding-based intent-aware search and personalization systems tuned to business user needs.

• Email Intelligence : Drive innovation in personalized outreach generation using context-aware generation pipelines.

Production-Grade Applied AI

• Latency & Cost Optimization : Tune inference pipelines caching layers and model selection logic for high-scale cost-aware performance.

• Evaluation at Scale : Define and drive robust offline and online testing methodologies (A/B sandboxing human evals) across agents and LLM flows.

• Feedback Loops : Architect human-in-the-loop systems and telemetry to improve accuracy UX and explainability over time.

What We’re Looking For

Technical & Production Depth

• 10+ years of software engineering experience with at least 3 years in applied LLM or agentic AI systems (2023–present).

• Proven success in deploying LLM-powered products used by real users at scale not just prototypes or internal tools.

• Deep backend & systems engineering expertise with Python distributed systems and scalable APIs.

• Familiarity with LangChain LlamaIndex or similar orchestration frameworks .

• Experience with RAG pipelines vector DBs embedding models and semantic search tuning.

• Experience managing performance across cloud providers (e.g. AWS Bedrock OpenAI Anthropic etc.).

Agentic Systems & Prompt Engineering

• Demonstrated experience building multi-step agents planning workflows chaining reasoning steps and integrating APIs with agent memory/state.

• Comfort with advanced prompting strategies few-shot and chain-of-thought reasoning and embedding retrieval setups.

Evaluation Monitoring & CI for AI

• Strong understanding of AI system evaluation human ratings A/B experimentation and feedback loop pipelines.

• Experience designing safety-aware reliable LLM systems in production environments.

• Experience owning logging monitoring and observability for live AI systems.

Leadership & Strategic Impact

• Principal-Level Ownership : You thrive in an ambiguous environment define company wide roadmaps drive the most important Engineering decisions and mentor others. You lead from the front.

• AI-Native Mentality : You leverage AI to ship faster and smarter and champion automation across engineering workflows.

• Applied Focus : You prioritize impact over novelty. You’re deeply pragmatic in your application of AI research to product features.

What Makes This Role Different

A Role with Real Autonomy

You’ll own complex systems end-to-end from LLM prompt design and API orchestration to production deployment and A/B testing at scale. You’re not building demos you’re shipping critical infrastructure that millions rely on.

A Product-First AI Culture

We believe in AI that moves the needle and your work will directly impact Apollo’s AI Assistants scoring models research agents and automation flows products that define our differentiation in the market.

The listed Pay Range reflects base salary range except for sales roles the range provided is the role’s On Target Earnings ('OTE') range meaning that the range includes both the sales commission/sales bonus targets and annual base salary for the role. This pay range may be inclusive of several career levels at Apollo and will be narrowed during the interview process based on a number of factors including the candidate’s experience qualifications and location. Applicants interested in this role and who are not located in the US may request the annual salary range for their location during the interview process.

Additional benefits for this role may include equity; company bonus or sales commissions/bonuses; 401(k) plan; at least 10 paid holidays per year flex PTO and parental leave; employee assistance program and wellbeing benefits; global travel coverage; life/AD&D/STD/LTD insurance; FSA/HSA and medical dental and vision benefits.

Annual Pay Range

$200000—$300000 USD