API Modernization Principal Engineer

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 skills and a One Team mindset across platform, infrastructure, AI, and product engineering organizations.

And It’s Great to Have

• Experience with gRPC, Protocol Buffers, GraphQL, or other strongly typed API frameworks.

• Familiarity with Model Context Protocol (MCP), AI orchestration systems, or building structured interfaces for LLM-powered tools and agents.

• Experience with event-driven architectures, workflow orchestration systems, and high-throughput distributed platforms.

• Experience establishing engineering standards, platform governance models, or enterprise-wide modernization initiatives.

• Experience designing highly observable systems with advanced traffic management, resiliency, and operational safeguards.

• Experience supporting AI-native product architectures or machine-driven integration ecosystems.

What Success Looks Like

• Core APIs are highly predictable, reliable, and scalable for both application teams and automated AI consumers.

• AI orchestration teams can integrate new agents and workflows with minimal custom integration logic or workaround layers.

• Platform standards for AI-ready APIs are clearly defined, practical to adopt, and consistently implemented across engineering organizations.

• Core systems remain stable, secure, and performant under increasing levels of automated and concurrent machine-driven traffic.

• Engineering teams have clear paved-path architectural guidance for building and evolving APIs that support long-term AI strategy.

• Modernization initiatives improve platform quality, reduce integration complexity, and accelerate AI capability delivery across ABC.

• The organization has a sustainable architectural foundation capable of supporting future AI-native platform evolution.

Why This Matters

ABC Fitness is building toward an AI-native future where intelligent agents, orchestration systems, and automation platforms can securely and reliably interact with our products and services at scale. The effectiveness of those systems depends on the quality, predictability, and reliability of the APIs that power them.

You are not simply modernizing APIs — you are helping build the operational foundation that allows AI systems to safely and effectively interact with ABC’s products, workflows, and data ecosystem at scale.

WHAT’S IN IT FOR YOU:

• Purpose led company with a Values focused culture – Best Life, One Team, Growth Mindset

• Time Off – competitive PTO plans with 15 Earned accrued leave, 12 days Sick leave, and 12 days Casual leave per year

• 11 Holidays plus 4 Days of Disconnect – once a quarter, we take a collective breather and enjoy a day off together around the globe. #oneteam

• Group Mediclaim insurance coverage of INR 500,000 for employee + spouse, 2 kids, and parents or parent-in-laws, and including EAP counseling

• Life Insurance and Personal Accident Insurance

• Best Life Perk – we are committed to meeting you wherever you are in your fitness journey with a quarterly reimbursement

• Premium Calm App – enjoy tranquility with a Calm App subscription for you and up to 4 dependents over the age of 16

• Support for working women with financial aid towards crèche facility, ensuring a safe and nurturing environment for their little ones while they focus on their careers

At ABC Fitness, we don’t just build technology—we build communities and transform lives. Your work matters here, your growth is supported, and your voice is heard. We welcome diverse talent and encourage you to apply, even if you don’t meet every requirement.

ABC’S COMMITMENT TO DIVERSITY, EQUALITY, BELONGING AND INCLUSION:  ABC is an equal opportunity employer committed to diversity, equity, and inclusion. We strive to create a workplace where every employee, client, and partner feels valued, inspired, and empowered to reach their full potential. For us, inclusion isn’t just the right thing to do—it’s a business imperative. Learn more at abcfitness.com.

About ABC Fitness

ABC Fitness is the #1 software provider for fitness businesses of any size, all around the world. Supporting 30K clubs, 650K coaches, 40M members, and processing more than $12B in payments every year, ABC Fitness provides scalable, data-driven solutions to simplify club management and engage members and clients.

From personal trainers, boutique studios, and gyms, to international franchise health clubs, ABC Fitness will move your business forward through technology and industry insights. Innovation is at the center of everything we do, across ABC Glofox, ABC Ignite, ABC Trainerize, and ABC Evo. Let's make your fitness vision a seamless reality, together. Learn more at abcfitness.com

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