Staff AI Engineer

Apollo.io is the leading go-to-market solution for revenue teams, trusted by over 500,000 companies and millions of users globally, from rapidly growing startups to some of the world's largest enterprises. Founded in 2015, the company is one of the fastest growing companies in SaaS, raising approximately $250 million to date and valued at $1.6 billion. Apollo.io provides sales and marketing teams with easy access to verified contact data for over 210 million B2B contacts and 35 million companies worldwide, along with tools to engage and convert these contacts in one unified platform. By helping revenue professionals find the most accurate contact information and automating the outreach process, Apollo.io turns prospects into customers. Apollo raised a series D in 2023 and is backed by top-tier investors, including Sequoia Capital, Bain Capital Ventures, and more, and counts the former President and COO of Hubspot, JD Sherman, among its board members.

About Apollo.io

Apollo.io is the leading go-to-market solution for revenue teams, trusted by over 500,000 companies and millions of users globally, from rapidly growing startups to some of the world's largest enterprises. Founded in 2015, the company is one of the fastest growing companies in SaaS, raising approximately $250 million to date and valued at $1.6 billion. Apollo.io provides an end-to-end go-to-market platform that enables sales and marketing teams to source prospects from our database of 210 million B2B contacts and 35 million companies, execute personalized email outreach campaigns, automate booking flows, and manage deals—all within one unified platform.

Apollo raised a Series D in 2023 and is backed by top-tier investors, including Sequoia Capital, Bain Capital Ventures, and more, and counts the former President and COO of Hubspot, JD Sherman, among its board members.

We are AI Native

Apollo.io is an AI-native company built on a culture of continuous improvement. We're on the front lines of driving productivity for our customers—and we expect the same mindset from our team. If you're energized by finding smarter, faster ways to get things done using AI and automation, you'll thrive here.

Your Role & Mission

As a Staff AI Engineer on our AI Engineering team, you will be responsible for building and productionizing advanced AI systems powered by Large Language Models (LLMs) and intelligent agents. You'll work on critical Apollo capabilities including our AI Assistant, Autonomous AI Agents, Deep Research Agents, Conversational Assistant, Semantic Search, Search Personalization, and AI Power Automation features that directly impact millions of users' productivity.

The mission of our AI teams is to leverage Apollo's massive scale data and cutting-edge AI to understand and predict user behaviors, personalize experiences, and optimize every stage of the customer journey through intelligent automation.

What You'll Be Working On

AI Assistant & Agent Systems

• Agent Architecture & Implementation: Build sophisticated multi-agent systems that can reason, plan, and execute complex sales workflows
• Context Management: Develop systems that maintain conversational context across complex multi-turn interactions
• LLM and Agentic Platforms: Build scalable large language model and agentic platforms that enable widespread adoption and viability of agent development within the Apollo ecosystem
• Backend Systems: Build back-end systems necessary to support the agents.
• AI features: Conversational AI, Natural Language Search, Personalized Email Generation and similar AI features

Classical AI/ML (Optional Focus)

• Search Scoring & Ranking: Develop and improve recommendation systems and search relevance algorithms
• Entity Extraction: Build models for automatic company keywords, people keywords, and industry classification
• Lookalike & Recommendation Systems: Create intelligent matching and suggestion engines

Key Responsibilities

• Design and Deploy Production LLM Systems: Build scalable, reliable AI systems that serve millions of users with high availability and performance requirements
• Agent Development: Create sophisticated AI agents that can chain multiple LLM calls, integrate with external APIs, and maintain state across complex workflows
• Prompt Engineering Excellence: Develop and optimize prompting strategies, underst