Senior Software Engineer

Fastn is on a mission to revolutionize how SaaS companies connect with their customers' environments. As a Senior Software Engineer, you will architect, develop, and scale an AI-powered integration infrastructure while leading and mentoring engineering teams to drive technical excellence.

Responsibilities:

• Architect & Build: Design and develop core infrastructure, APIs, and integration workflows that power Fastns platform
• Scalability & Performance: Build and optimize distributed systems that handle millions of transactions per second/minute with sub-millisecond response times
• AI-Powered Integrations: Leverage AI-driven automation, data mapping, and smart API connectivity to enhance the integration experience
• Security & Compliance: Implement industry-best practices for API security, data privacy, and regulatory compliance (SOC 2, GDPR, etc.)
• Technical Leadership: Lead and mentor teams, fostering a culture of high performance, innovation, and technical excellence
• Collaboration: Work cross-functionally with product, design, and customer success teams to create a world-class developer experience
• Strategic Impact: Influence product and technology strategy, ensuring Fastn remains at the forefront of AI-powered integration infrastructure

Requirements:

• 5+ years of software development experience, ideally in high-performance SaaS platforms, API infrastructure, or distributed systems
• Proven track record of building and leading engineering teams in high-growth environments
• Strong expertise in backend development using Java, Python, or Node.js (Fastn's stack is flexible)
• Deep knowledge of high-performance, low-latency systems with sub-millisecond response times
• Experience designing and working with RESTful and GraphQL APIs
• Expertise in database design & optimization (PostgreSQL, DynamoDB, or similar) for massive-scale applications
• Experience with cloud platforms (AWS, GCP, Azure) and serverless architectures
• Knowledge of event-driven architectures and message queues (Kafka, RabbitMQ, etc.) for handling millions of transactions per second/minute
• Strong understanding of API security & authentication (OAuth, JWT, OpenID)
• Experience with AI/ML-driven automation in integrations is a plus
• Experience with iPaaS (Integration Platform as a Service) tools like Mulesoft, Workato, or Tray.io
• Hands-on experience with distributed systems and real-time data processing pipelines
• Previous work in developer tooling, B2B SaaS integrations, or API marketplaces