What is an API-First Product Engineer?
Tom Smykowski is a senior staff and product engineer based in Poland, specializing in API-first development for SaaS and enterprise products. With nearly two decades of experience, he combines deep technical architecture skills with product and UX thinking to build scalable, maintainable, and user-centric API ecosystems. Hiring an API-first product engineer like Tom is ideal for founders, CTOs, and executives who need ownership from initial discovery and API design through to production deployment and iteration, ensuring the technical foundation drives business value.
An API-first product engineer approaches system design by defining the contract first. This means designing robust, well-documented APIs before writing implementation code, ensuring consistency, developer experience, and future scalability. This methodology is critical for multi-tenant SaaS platforms, microservices architectures, and products that require seamless integration with third-party services or have complex frontend-backend interactions. Tom's experience spans from founding his own fintech SaaS, Websoul, serving 32,000+ businesses, to staff engineering roles at scale-ups like Croissant and Printify, where API design was central to product strategy and compliance.
This role goes beyond backend development. It encompasses the full product lifecycle, requiring collaboration with product managers, designers, and other engineers to translate business requirements into a coherent technical vision. The outcome is a product where the API is not an afterthought but a primary asset, enabling faster frontend development, easier partner integrations, and a more resilient and evolvable system architecture. For teams building or modernizing subscription platforms, marketplaces, or data-intensive applications, an API-first approach led by an experienced engineer is a strategic advantage.
Building Scalable API Architectures for SaaS
Scalability in SaaS is not just about handling more users, it is about designing systems that can grow in complexity without becoming unmanageable. An API-first approach is foundational to this. Tom has architected and evolved systems for products like Printify's design system, which supported a rebrand ahead of a major merger and served a platform with over 10 million merchants. In such environments, the API layer dictates how data flows, how services communicate, and how new features can be safely introduced without breaking existing functionality.
The technical strategy involves careful consideration of API patterns, such as REST, GraphQL, or gRPC, based on the product's specific needs. It also involves designing for multi-tenancy, secure data isolation, rate limiting, and comprehensive observability. At Croissant, a workplace platform, Tom worked on compliance and collaboration features where API design directly impacted security and user experience. This experience translates to building APIs that are not only performant but also adhere to regulatory standards and facilitate seamless client-side development, a critical factor for distributed teams.
Implementing a scalable API architecture requires tools and practices that promote consistency and quality. This includes API specification languages like OpenAPI, automated documentation generation, contract testing, and a strong CI/CD pipeline. By establishing these practices early, teams can avoid the common pitfalls of inconsistent endpoints, poor documentation, and brittle integrations. Tom's work emphasizes creating developer-friendly APIs that accelerate internal development and empower external partners, turning the API into a product in itself that drives platform adoption and ecosystem growth.
From Product Discovery to API Contract Design
The journey of an API-first product begins long before the first line of code is written. It starts in the discovery phase, where business goals, user stories, and system boundaries are defined. As a product-minded engineer, Tom engages deeply in this phase, working with stakeholders to identify core entities, operations, and data models. This collaborative process ensures the API design reflects true business capabilities and user needs, not just technical convenience. The output is a clear API contract that serves as a single source of truth for all teams involved.
Designing the contract involves making critical decisions about resource naming, HTTP methods, response formats, error handling, and versioning strategy. These decisions have long-term implications for maintainability and developer experience. For instance, at Websoul, building a marketing automation and fintech SaaS required designing APIs that could handle complex data grids, real-time updates, and secure financial operations. Using technologies like TypeScript, Supabase, and AG Grid, Tom established patterns that made the frontend development predictable and efficient, demonstrating how a well-designed API contract reduces integration friction.
This phase also includes planning for evolution. Products change, and APIs must be able to evolve without disrupting consumers. Strategies like semantic versioning, backward-compatible changes, and clear deprecation policies are integral to the design. By socializing the API contract early with frontend, mobile, and potential integration teams, an API-first product engineer validates assumptions and gathers feedback, reducing rework later. This proactive, collaborative approach to API design is what separates a functional endpoint from a strategic platform component that enables rapid and reliable product development.
Integrating Frontend UX with Robust Backend APIs
A superior product experience is achieved when the frontend UX and backend API are designed in concert. An API-first product engineer ensures the API provides the exact data and operations the UI needs, in an optimal format, minimizing client-side logic and network requests. Tom's extensive frontend expertise, including deep work with Vue.js, TypeScript, and design systems, informs his API design. He understands the components, state management, and data-fetching patterns modern frontends use, allowing him to craft APIs that feel natural for frontend developers to consume.
This integration is particularly important for complex, data-rich interfaces like admin dashboards, data visualization tools, or real-time collaboration features. For example, at Fream, an industrial SaaS, Tom led frontend development involving maps and conversion-focused UX. The underlying APIs had to deliver geospatial data efficiently and support interactive user journeys. Similarly, at Printify, supporting a design system used by around 60 frontend engineers necessitated APIs that were consistent, well-documented, and aligned with the component library's data requirements. This tight coupling accelerates feature development and improves performance.
The practice also extends to developer tooling and workflows. By generating TypeScript definitions from the API specification, frontend teams get autocompletion and type safety, catching errors at compile time rather than runtime. Implementing patterns like HATEOAS or GraphQL can further empower frontend teams to fetch nested data in a single query. An API-first product engineer bridges the traditional gap between frontend and backend teams, fostering a unified product development culture where the API is the central collaboration point, leading to faster iterations and a more cohesive final product.
API-First Development for AI and Modern Workflows
The rise of AI and agentic workflows has created new demands on API design. AI-native applications often rely on orchestrating multiple services, handling streaming responses, and managing stateful interactions. An API-first mindset is essential to building predictable and integrable AI capabilities into a product. Tom's work in AI-assisted workflows and consulting on AI Software Factory setup positions him to design APIs that are not just for CRUD operations but for complex cognitive tasks, reasoning, and automation.
This involves designing for new paradigms, such as endpoints that return structured JSON conforming to a specific schema for agent consumption, or implementing server-sent events for streaming LLM responses. It also means building robust abstraction layers so that the underlying AI model provider can be swapped without affecting all API consumers. Security and cost management become paramount, requiring API design that includes proper authentication, usage tracking, and budget controls. For products looking to embed AI features, the API is the gateway that determines how easily and safely these capabilities can be used.
Furthermore, modern engineering workflows themselves benefit from API-first principles. Internal tools for CI/CD, monitoring, and developer productivity can be built as reusable services with clear APIs. Tom's focus on developer experience and AI adoption includes setting up automated quality gates, AI coding agents, and efficient SDLC processes, all of which rely on well-defined internal APIs. By applying product engineering principles to these internal platforms, he helps engineering teams become more productive and maintain high code quality, ultimately speeding up the delivery of customer-facing features.
When Hiring an API-First Product Engineer is a Good Fit
Engaging a senior API-first product engineer like Tom is a strategic move for specific scenarios. It is an excellent fit when your team is building a new SaaS product or a major new platform module and you need to establish a solid, scalable foundation from the start. It is equally valuable when modernizing a legacy monolith into a microservices or service-oriented architecture, where defining clear service boundaries and contracts is critical to success.
This role is also highly beneficial when you have a growing product with increasing integration needs, either with third-party partners or between internal teams, and you need to professionalize your API strategy to reduce friction and support growth. If you are incorporating AI features and need to design APIs that are secure, cost-effective, and easy for both human developers and automated agents to use, this expertise is crucial. Finally, if you are a founder or CTO who needs a staff-level engineer to take full ownership of the technical product vision, from API design through implementation and team mentorship, this is the ideal profile to drive your project forward with both technical excellence and product sense.