Software Engineer II

Mastercard Mastercard · Fintech · O Fallon, MO +1 · Engineering

Software Engineer II at Mastercard to design and build the next-generation Decision Management Platform, a real-time system for scoring and approving payment transactions. The role involves writing production code, designing distributed systems, and utilizing AI coding tools to improve development speed and quality. Responsibilities include making technical calls on frameworks, sharing AI tool usage patterns, and improving system performance, reliability, and cost-efficiency. The role also involves cross-team collaboration, mentoring, and interviewing.

What you'd actually do

  1. Write production code for services, tooling, and platform features.
  2. Pick the right frameworks, libraries, and tools by weighing quality, cost, latency, and reliability.
  3. Use AI coding tools as your default way of working.
  4. Make the customer experience better across the services you work on.
  5. Contribute to designs that span multiple services.

Skills

Required

  • Several years of software engineering experience with real contributions to complex systems or shared platforms.
  • Hands-on experience with distributed systems running at high throughput and sub-second latency.
  • Solid grasp of modern software engineering practices, cloud-native architectures, and AI/data platforms.
  • Clear communicator who works well across teams.
  • Bachelor's degree in Computer Science, Software Engineering, or a related field — or equivalent experience.

Nice to have

  • Experience at a startup or in a startup-like environment inside a larger company
  • Comfortable working in several languages and eager to pick up new ones, frameworks, and tools
  • Advanced degrees are a plus

What the JD emphasized

  • high-throughput, low-latency systems
  • real-time decisioning
  • AI coding tools
  • low-latency inference

Other signals

  • AI coding tools
  • LLM integration
  • prompt engineering
  • agentic patterns
  • model monitoring
  • low-latency inference