Product Engineer, Experience

About Callimacus

At Callimacus, we're working to change how people interact on the web. For the past 30 years, the user experience as we know it has been anchored to a typographic paradigm — predefined navigation trees of pages, sections, and menus — established in the Nineties when the web was born.

As the way people get informed, entertained, and shop evolves, traditional websites and interfaces are losing relevance, and the tools available limit the creative evolution of digital experiences. Callimacus was born from the conviction that the whole web experience can and should be reinvented.

So we built the engine for a different kind of digital experience. Callimacus is a multi-agentic platform that plugs into a company's existing stack and reads multi-dimensional signals to understand what a visitor wants in the moment. Then, in milliseconds, our proprietary technology composes the entire interface around that intent, selecting the most relevant content and components as the person interacts.

Callimacus was founded in 2024 with the early backing of Brunello Cucinelli — one of our first investors, and now one of our customers. We launched in January 2026 to strong organic interest from enterprise customers, and recently raised from Salesforce Ventures the largest AI investment they have made in Italy, and one of their most significant in Europe.

We are a small, product-focused, founder-led team. We work on hard problems that haven't been solved before — by us or anyone else — and the people who join now get to solve them. We move fast, with high agency and strong ownership.

What you'll build

You'll join a small senior team at the point where the platform's foundations are still being set. Callimacus is in production with demanding customers, and the architecture, the performance envelope, and the shape of the developer experience are all still yours to influence. Decisions you make in your first months will still be load-bearing in three years.

• Own the rendering path. The pipeline that turns composed output into an experience that feels immediate — streaming, hydration, and perceived performance on sites we don't control.
• Build the SDK customers integrate. The TypeScript SDK that drops into enterprise frontends — API design, developer experience, and documentation people actually enjoy using.
• Design the component and composition system. Interfaces assembled on the fly by agents still have to feel deliberate and on-brand. You make that true.
• Sweat the performance envelope. Core Web Vitals, bundle discipline, and edge delivery — on our customers' sites, under their traffic.
• Shape the integration experience. From first npm install to production, across stacks and frameworks we don't choose.

What matters to us

These are the same for every role at Callimacus. We hire people who get the job done and care about the end result — the product, the experience, the people using it.

• Ownership. You feel deeply responsible for your work and behave accordingly — from design through production and after. You don't wait to be told what to do; you see problems and act. "It's not my job" is not part of your mindset.
• Invention. You light up at hard problems and are creative at finding solutions. You experiment, get your hands dirty, and land things. You hold very high standards and always look for ways to improve.
• Team-oriented. You're someone others can count on. You support the best idea even when it's not yours, disagree productively, give and take feedback, share credit, and take on unglamorous work when that's what the team needs.

The craft bar for this role: Strong TypeScript and deep React knowledge, with a track record of shipping polished production frontends. You treat developer experience as a product surface, not an afterthought.

Where you might be strong

We're early, and nobody is strong in all of these — we don't expect you to be. Depth in two or three, plus curiosity about the rest, is what wins. If that's you, apply even if you don't tick every box.

• SDK, API, or developer-platform design with real attention to DX
• Rendering performance and Core Web Vitals
• Design systems and component architecture
• Streaming or real-time interfaces
• Edge delivery and distributed frontends
• Documentation, examples, and integration tooling

Bonus points

• Experience as an early engineer at a startup or fast-growing company&