Software Developer III, Application Security

United States Information Technology

Mailgun is hiring a Senior Software Developer to join our Application Security Team. The team’s mission is to protect our customers from unauthorized use of their accounts by implementing state of the art security measures. Our ideal candidate is a full stack engineer with a passion for security, a jack-of-all-trades who can figure out how to protect every component of the system from a wide range of attacks.

We have a distributed engineering team and will consider qualified candidates in the following countries: United States, France, Germany, UK, Spain

Our Team

  • We move fast and don’t believe in having unnecessary silos and red tape that keep teams from shipping software. As a developer on the team, you are responsible for not only building great software, but ensuring it is operating properly once it’s been deployed.
  • We have a passion for solving hard problems – our services are responsible for processing billions of requests each day and have to not only scale, but be highly secure.
  • The Application Security Team is dealing with an adversarial problem, which means it’s a dynamic environment with constantly changing requirements.


  • Monitor security vulnerabilities coming from the bug bounty program.
  • Secure API endpoints and customer-facing UI from a wide range of attacks.
  • Implement security measures against credential compromises and account takeovers.
  • Maintain and improve existing authentication and authorization mechanisms.
  • Develop services that proactively invalidate exposed credentials.
  • Perform proactive research and threat modeling to detect new attack vectors.
  • Perform reactive incident response when a security event occurs.
  • Being a subject matter expert on the latest security practices and threat landscape.


  • Experience with RESTful web services.
  • Experience working with Javascript, Python or Go.
  • Experience working with MongoDB and/or Cassandra is preferred.
  • Experience building scalable distributed systems is preferred.
  • Experience with SQL and noSQL (Mongo, Cassandra) databases is preferred.
  • Experience with both front-end and back-end development is preferred.
  • Passion for clean and simple code despite tight time constraints.


  • 5+ weeks PTO (treat yo’ self)
  • 8 paid holidays
  • Up to 100% Medical coverage for employees
  • Life insurance
  • Exclusive Gold’s Gym membership discounts
  • 12 weeks paid Maternity Leave for birth mothers
  • 4 weeks paid Parental Leave for parents, including through adoption or foster care
  • 401k with employer match


Powerful Transactional Email APIs that enable you to send, receive, and track emails, built with developers in mind.

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