Senior AI Engineer

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 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 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 Hub Spot, JD Sherman, among its board members.

As a Senior AI Engineer on our AI Engineering team, you will be responsible for building and product ionizing 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.

• 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.

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

• 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, understand trade‑offs between prompt engineering vs fine‑tuning, and implement advanced prompting techniques.
• System Integration
  :
  Build robust APIs and integrate AI capabilities with existing Apollo infrastructure and external services.
• Evaluation & Quality Assurance
  :
  Implement comprehensive evaluation frameworks, A/B testing, and monitoring systems to ensure AI systems meet accuracy, safety, and reliability standards.
• Performance Optimization
  :
  Optimize for cost, latency, and scalability across different LLM providers and deployment scenarios.
• Cross‑functional Collaboration
  :
  Work closely with product teams, backend engineers, and stakeholders to translate business requirements into technical AI solutions.

• 8+ years of software engineering experience with a focus on production systems.
• 1.5+ years of hands‑on LLM experience (2023‑present) building real applications with GPT, Claude, Llama, or other modern LLMs.
• Production LLM Applications
  :
  Demonstrated experience building customer‑facing, scalable LLM‑powered…