Full Stack Engineer III

Calendly

4d•$156,400 - $227,424

About The Position

Calendly’s Trust & Safety team protects hosts, invitees, and messaging providers by preventing and responding to abuse, protecting the deliverability and compliance of email and SMS, and keeping messaging costs predictable. The team addresses adversarial activity by evaluating behavior, patterns, and content, building durable signals, and carefully balancing abuse prevention against false positives. Engineers work closely with Trust & Safety Operations, which encounters abuse firsthand and helps shape the team’s solutions. The Full Stack Engineer builds and improves systems that detect and stop abuse across sign-up, booking, and messaging, including spam, phishing, bots, and fraudulent SMS traffic. The role also improves notification reliability, deliverability, and compliance; carefully evaluates detection systems against real traffic; responds to active abuse, including through on-call; and builds tools that help Operations review accounts and understand system decisions. The engineer partners with Product, Operations, Data, and other product teams, and contributes to implementation reviews, pull-request reviews, and team learning. The position reports to the Engineering Manager for the Trust & Safety team.

Requirements

At least 3 years of professional software development experience at a SaaS or technology company, including building and operating production systems.
Strong backend skills, including building services, APIs, and data-heavy workflows in a service-oriented architecture.
Experience with Rails, Node/TypeScript, Go, or a comparable language or framework, and willingness to work across more than one.
Comfort with relational databases and SQL, and using data to evaluate whether changes worked.
An analytical, curious mindset and the ability to consider how systems could be misused.
Good judgment about trade-offs, including preventing abuse without adding friction for legitimate customers.
Commitment to clean, reliable, maintainable code, thoughtful testing, and shipping in small increments.
Clear communication with technical and nontechnical partners, including Operations and Support.
Comfort and skill using AI tools in engineering work, including critically reviewing their output.
Availability to participate in an on-call rotation for critical services.
Authorization to work lawfully in the United States; Calendly does not provide immigration sponsorship at this time.

Nice To Haves

Experience in trust and safety, fraud, spam, or abuse prevention.
Experience with email or SMS delivery, such as deliverability, sender reputation, or messaging compliance.
Experience with bot protection, rate limiting, or third-party risk and verification services.
Experience building rules engines, risk scoring, or ML-backed decisions in production.
Experience using LLMs to classify or moderate user-generated content.
Experience with GCP, Kubernetes, PostgreSQL, or Redis.

Responsibilities

Build and improve systems that detect and stop abuse across sign-up, booking, and messaging, including spam, phishing, bots, and fraudulent SMS traffic.
Improve the reliability, deliverability, and compliance of Calendly email and SMS notifications.
Evaluate new detection systems on real traffic before they act on accounts, balancing false positives against false negatives.
Respond to active abuse, including during on-call, stop damage quickly, and replace short-term fixes with durable solutions.
Build tools that help Trust & Safety Operations review accounts faster and understand why the system took each action.
Partner with Product, Operations, and Data to define requirements and measure the impact of shipped work.
Work with other product teams to add protections to the flows they own.
Review implementation plans and pull requests, and share learnings with the team.