Web3 Engineering Jobs in London, United Kingdom

About Us

OpenFX is on a mission to move money as freely as data, unrestricted by time zones, banking hours, or legacy systems. We are building the infrastructure that will power the next generation of cross-border payment systems for institutions. The team's execution has been exceptional, and we're scaling at a remarkable pace. Our stellar early team comes with experience in companies like J.P. Morgan, Goldman Sachs, FalconX, Paypal, Affirm, Polygon, Kraken, Nium & others. We’re backed by Accel, Lightspeed, NfX and other top-tier investors.

Role Overview

We are seeking a Developer Experience Lead, who will report to the head of Product Growth, to own the entire developer-facing surface of our platform, from documentation to integration support to API governance. We have built a world-class financial engine, but how external developers experience that engine has no owner. This role fills that gap.

This is a foundational role. You will be the first hire in this function. You will architect the documentation ecosystem from the ground up, define the processes that keep it accurate as the platform evolves, and directly support the clients who integrate with our APIs. Over time, you will shape how Developer Experience operates as a discipline at OpenFX, influencing product decisions, integration strategy, and the developer journey end-to-end.

You will set the bar higher than industry standards, building a knowledge system that turns complex FX liquidity and cross-border payment flows into a Hello World integration in under 15 minutes.

Key Responsibilities:

• Drive API Product Adoption
  • You own API adoption as a measurable outcome. You instrument the funnel from API key activation to first API call to first transaction to expanded endpoint usage. You set the baseline, define the targets, and drive the cross-functional work to move the number. Every quarter, more developers are activated, more endpoints are used, and integrations go deeper. This is what you are accountable for, not pages shipped.
• Architect the Documentation System
  • Documentation is the primary adoption surface. You own the docs-as-code infrastructure that engineers can contribute to. You measure documentation by whether it moves adoption, not by completeness for its own sake.
• Own the OpenAPI Workflow
  • Your first technical priority is aligning the OpenAPI spec to production reality. Then you implement and enforce a contract-first governance model where the spec is treated as a product contract, not a generated afterthought. Spec linters run in CI as merge blockers. OpenAPI updates are part of engineering's Definition of Done. Breaking changes are detected automatically and routed through a defined deprecation process. You sit in Product and Engineering reviews as the First User: if an API is too hard to explain in writing, it is too hard to use, and you have the authority to push back before code ships.
• Drive Developer Advocacy
  • You are the external voice of OpenFX inside the developer community and the internal voice of the developer inside OpenFX. You write technical content that earns developer trust: deep-dive blog posts on idempotency under retries, sample apps that demonstrate real cross-border payment flows, integration pattern guides for PSP, neo-bank, and treasury use cases. You build feedback loops that turn integration friction into product changes. As volume justifies, you represent OpenFX at developer-focused events, conferences, and partner enablement sessions. You are the reason developers choose OpenFX over a competitor whose docs they could not understand.
• Own Integration Triage
  • You are the technical front door for client integration questions during US business hours. You triage whether each issue is a documentation gap, an API design problem, or a code bug. You fix documentation gaps directly and route the rest to engineering with structured context. You build the repeatable onboarding playbook that turns one-off Slack threads into a scalable process. You partner with GTM, who owns the client relationship; you own the developer experience surface that surfaces during integration.

What Success Looks Like

• API Product Adoption: You own the adoption funnel from API key activation to first API call to first transaction to expanded endpoint usage. You instrument it, set the baseline, define the target, and drive the cross-functional work to move the number. This is the metric you are accountable for.
• Time to First API Call: Drops from around 3 days to under 15 minutes within 90 days. You own the Quickstart, code snippets, and onboarding tutorials that make this speed possible, and you advocate for the product changes needed to remove the rest of the friction.
• Instructional support tickets: reduced 40% within 90 days, with 42% of onboarding support requests as the baseline.
• Spec drift: no spec drift incidents that reach production. The OpenAPI spec stays aligned to production as the platform evolves.
• V1 Developer Portal: a public API doc portal (References, Guides, Changelog, sample apps) is live, searchable, and built on docs-as-code infrastructure. 100% of public endpoints have accurate request and response examples.
• Developer advocacy presence: a published cadence of technical content (deep-dive guides, sample apps, integration patterns) that builds developer trust and drives inbound adoption. Establish the baseline, grow it quarterly.
• DX roadmap: a written plan for SDK strategy, portal evolution, adoption analytics, and Agent Experience foundations and expansion (CLI, MCP)

What we are looking for

Must-haves:

• 5+ years owning a developer-facing API product or platform. B2B or infrastructure. You drove a measurable adoption outcome, not just shipped pages. You can point to the integration experience you built, the funnel you owned, and the metric you moved.
• Direct client integration work. You have sat on integration calls with B2B or institutional clients, diagnosed friction live, and fed it back into product changes (not just documentation updates). You know what breaks during real integrations, not what should break in theory.
• Product instinct for API design. You have opinions on endpoint design, parameter naming, authentication UX, error response formats, idempotency keys, and SDK ergonomics. You have opinions on these calls and get changes shipped before code hits production.
• Engineering fluency. You read code well enough to extract logic independently. You understand distributed system concepts (latency, rate limiting, idempotency, eventual consistency, async patterns). You can sit in a code review and have something useful to say.
• Contract-first governance experience. You have implemented or enforced OpenAPI workflows where the spec is treated as a product contract, not a generated artifact.
• Financial services or fintech context. You know the difference between authorized and settled. You have worked on payments, trading, or banking APIs.
• Agent Experience instinct. You have shipped or experimented with MCP servers, agent-native SDKs, llms.txt, evaluation suites for LLM-driven API consumption, or other agent-readable API patterns. You have a point of view on what Developer Experience looks like when AI agents are first-class consumers.

What helps you stand out:

• Interactive docs experience: code playgrounds, Try It Now, in-browser sandbox.
• Multimedia documentation skills: video tutorials, sequence diagrams, architecture diagrams that complement written documentation.
• Developer advocacy or DevRel experience: you have written technical content for an external developer audience, shipped sample apps, or represented a product at developer events.

What We Offer

• Competitive salary and benefits package.
• Equity in a rapidly growing company.
• Opportunity to work in a fast-paced startup at the forefront of fintech innovation.
• Opportunity to make a significant impact on global financial infrastructure
• Collaborative work culture with emphasis on personal and professional growth.

We are committed to building a diverse and inclusive workplace. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability, or veteran status.