Principal AI Engineer – API Modernization (AI & Agent Systems)

Join ABC Fitness and become part of a culture that’s as ambitious as it is authentic. Let’s transform the future of fitness—together!

Our Values

Best Life

We believe great work begins with great people. That’s why our culture is built on respect, trust, and belonging. We create an inclusive environment where every team member can bring their authentic self to work—because diverse perspectives drive innovation and meaningful impact.

Growth Mindset

We are doers, thinkers, and dreamers. At ABC Fitness, your growth is our investment. Through continuous learning, mentorship, and professional development opportunities, we empower you to reach new heights—personally and professionally.

One Team

From day one, you’ll be part of a team that collaborates, celebrates, and cares. We move fast, support one another, and have fun along the way. Because when you thrive, we all thrive.

What You’ll Do

• Lead modernization efforts for core APIs and platform interfaces that support AI-native workflows and automated consumers.
• Define and drive company-wide standards for AI-ready APIs, including deterministic behavior, schema consistency, validation, observability, versioning, and operational safeguards.
• Refactor and evolve legacy systems to support structured machine consumption, orchestration layers, MCP integrations, and scalable agent workflows.
• Identify and resolve API inconsistencies such as non-standard error handling, hidden side effects, ambiguous data models, and weak contract enforcement.
• Design backend systems and APIs capable of supporting high-concurrency automated traffic patterns, orchestration loops, and resilient distributed workflows.
• Establish architectural guardrails including idempotency protections, advanced rate controls, validation strategies, authorization patterns, and failure containment mechanisms.
• Partner with AI orchestration teams, platform engineering, and domain engineering organizations to enable scalable integration patterns across ABC’s ecosystem.
• Provide technical leadership and architectural guidance across multiple engineering organizations while helping shape long-term modernization strategy.
• Lead design reviews, mentor senior engineers, and help elevate engineering standards and architectural maturity across the company.
• Develop pragmatic modernization strategies that balance ideal future-state architecture with operational realities, production constraints, and incremental delivery goals.
• Drive alignment between platform architecture, API strategy, and AI enablement initiatives across the organization without disrupting existing product and operational roadmaps.

What This Is Not

• Not building isolated greenfield services that do not connect to core business systems.
• Not a traditional feature-delivery role focused primarily on frontend or UI-driven requirements.
• Not incremental bug fixing — this is a strategic modernization and re-architecting effort focused on core platform interfaces and machine interoperability.

What You’ll Need

• Typically 10+ years of software engineering experience with deep expertise in backend systems, distributed architectures, and platform engineering.
• Demonstrated success architecting, building, and evolving complex APIs and distributed systems at scale.
• Proven experience modernizing legacy platforms and mission-critical production systems without disrupting business operations.
• Deep understanding of API contracts, schema design, deterministic behavior, observability, validation, versioning, authentication, authorization, and integration reliability.
• Strong systems-thinking mindset with the ability to understand platform-wide architectural implications and downstream effects on AI agents and orchestration systems.
• Experience driving technical strategy and influencing architectural direction across multiple teams and organizations.
• Strong engineering fundamentals across resiliency, scalability, performance, operational excellence, and distributed systems design.
• Ability to operate as a senior technical leader and subject matter expert within a complex engineering organization.
• Experience mentoring senior engineers and leading architectural discussions that improve platform quality and long-term maintainability.
• Pragmatic decision-making skills with the ability to balance strategic architecture goals with delivery timelines and existing system constraints.
• Strong collaboration ski…