Senior Engineer I (Fraud)

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.

Your Role & Mission

This role sits at the intersection of backend engineering, security, and fraud operations, and will play a critical role in evolving Apollo’s abuse detection and account security capabilities.

As a Senior Engineer I (Fraud), you’ll work closely with Fraud Operations, Data Science, Application Security, and Product to modernize abuse detection logic, prototype and deploy new risk decisioning systems, and build the technical foundation for a fraud decision engines over the next several quarters. This role is ideal for a senior engineer who thrives in ambiguous, data-driven problem spaces and enjoys building systems that directly protect customers and the business.

Daily Adventures & Responsibilities

• Lead the implementation and ongoing improvement of abuse detection services and customer account security features

• With assistance of team manager, implement a home-grown risk decision engine

• Build and maintain APIs to support extensible, low-latency risk decisioning

• Research and analyze abuse tools and attacker tactics to inform detection strategies

• Participate in fraud incident triage and lead development of mitigations and remediation

• Collaborate with Data Science and Data Engineering on model feature design

• Work closely with Fraud Operations and Application Security to align detection and response

• Stay informed on fraud prevention trends and apply relevant insights internally

Skills & Relevant Experience

• 5+ years building production backend systems in a SaaS or similar environment

• Experience designing scalable backend services; exposure to risk or decisioning systems a plus

• Proven track record of designing customer-first features

• Ability to explore and validate ideas using imperfect or partially structured data

• Strong foundation in secure system design and layered defenses

• Comfortable presenting designs to both technical peers and senior stakeholders

• Familiarity with common abuse vectors, evasion techniques, or scraping patterns

• Strong ownership mindset and ability to prioritize effectively

• Fraud, trust & safety, or security-adjacent experience preferred

• Clear written and spoken English communication

Our tech stack is React/Redux/NodeJS on the frontend, Ruby/Ruby on Rails/MongoDB/Elasticsearch on the backend, and Kubernetes/Docker/Ansible/Terraform in infrastructure.

Apollo.io Tech Blog: Deep dives into engineering, product design, and company-culture stories from the Apollo team, offering behind-the-scenes insight into how Apollo builds and scales its B2B sales platform.

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.

Why You’ll Love Working at Apollo

At Apollo, we’re driven by a shared mission: to help our customers unlock their full revenue potential. That’s why we take extreme ownership of our work, move with focus and urgency, and learn voraciously to stay ahead.

We invest deeply in your growth, ensuring you have the resources, support, and autonomy to own your role and make a real impact. Collaboration is at our core—we’re all for one, meaning you’ll have a team across departments ready to help you succeed. We encourage bold ideas and courageous action, giving you the freedom to experiment, take smart risks, and drive big wins.

If you’re looking for a place where your work matters, where you can push boundaries, and where your career can thrive—Apollo is the place for you.

Learn more here!