Join us and help us transform the investment sector with Slate WT. We are looking for someone to join us as Product Engineer. Our goal is to make investing easier, and this role will contribute to improving the overall operations and experience of our clients.
The role
Reporting to Engineering Lead / CTO, we're looking for an engineer who thinks like a product person and codes like a senior developer.
You won't be handed specs to implement. You'll work alongside the Product Manager as a technical partner — contributing to conversations about what gets built and why, surfacing complexity early, and challenging assumptions before they become costly. The PM owns the roadmap and the client relationships;
you own the technical translation: the API contracts, the architectural decisions, and what actually ships. Then you build it, maintain it in production, and feed what you learn back into the next cycle.
The technical depth is real: our stack is Kotlin + Spring Boot on a hexagonal architecture, AWS SQS for async event flows, multi-tenant production systems across regulated financial markets. You need to be comfortable there. But what separates this role is the ability to understand the *why* behind a feature and carry that context through to the implementation.
AI fluency is expected as table stakes — you should already be using AI tools daily to move faster and think harder. The goal isn't AI for its own sake;
it's being the kind of engineer who delivers more than the team expects, reliably.
What you'll do
Work closely with the Product Manager on feature definition: bring technical perspective to scoping discussions, flag complexity trade-offs early, and make sure what lands on the roadmap is actually the right thing to build.
Design and own the API contracts within your domain — APIs that external developers integrate into their financial products, where clarity, stability, and usability matter as much as correctness.
Build and maintain backend microservices (Kotlin + Spring Boot) powering financial operations: trading,



portfolio, cash, KYC.
Make architectural decisions within your domain;
bring proposals to the team rather than waiting for direction.
Work with async messaging (AWS SQS) to handle event-driven financial data flows across multiple tenants.
Integrate third-party providers (brokers, custody services, market data APIs) and make those integrations robust under failure conditions.
Use AI coding tools (Claude Code) as a standard part of your workflow — prototyping, refactoring, reviewing, documenting.
Spot where LLM-powered capabilities could improve product or internal tooling, and prototype them without needing permission.
Participate in incident response and on-call for production services that real financial clients depend on.
What we’re looking for
Must have:
4+ years building production backend systems — you've shipped things that ran in production and dealt with what came after.
Strong Kotlin and/or Java skills;
comfortable with modernJava (21+) and idiomatic Kotlin.
Hands-on experience with Spring Boot and building RESTful / event-driven services.
Solid understanding of DDD and hexagonal / clean architecture patterns.
Product instinct: you can articulate *why* a feature should exist, push back on scope that doesn't hold up, and make trade-off calls without constant oversight.
Good API design sense — you've designed APIs that other developers consume and you care about the experience of using them.
Daily use of AI coding assistants (Claude Code, Cursor, Copilot, or similar) — already part of how you work, not something you're planning to explore.




Ability to run autonomously in a small team with minimal process overhead.
Experience in a B2B product context — working directly with technical clients or integration partners, not just internal consumers.
Background in fintech: trading, payments, KYC/AML, regulatory compliance (MiFID II), or financial data processing.
Experience with LLM APIs (Anthropic Claude, OpenAI) — building features that call, orchestrate, or evaluate LLM outputs.- Practical knowledge of AWS SQS (or similar queuing/messaging systems) and async message processing.
Working experience with PostgreSQL, Redis, and/or MongoDB in production.
Cloud-native experience on AWS — EKS, IAM, S3, RDS.
Comfort with GitLab CI/CD, Kubernetes, and container-based infrastructure.
How we work
Remote-first. We communicate async and document decisions — meetings are the exception.
AI-augmented by default. We expect engineers to use AI tools actively and to raise the bar of what they can deliver individually.
Product-minded engineering. We don't draw a hard line between "product" and "engineering" — good engineers here understand the business context of what they build.
Competitive salary based on experience.
Hybrid work. Flexibility to work remotely and from our office in Madrid. We care more about your work ethic and attitude than your location.
Paid health insurance.
English and French classes.
Career development opportunities within the company.
At Slate WT, we believe in equal opportunities and value diversity. Whatever your personal circumstances may be, we would love to learn more about you.
In accordance with Regulation (EU) 2016/679 (GDPR), we inform you that your personal data will be processed by SLATE WEALTH, S.L. for the purpose of including your application in our recruitment and selection processes. You may exercise your data protection rights by contacting Additional information about the processing of your personal data can be found in our Privacy Policy available at

📌 Product Engineer (Backend) (Madrid)
🏢 Slate Wealth Technology
📍 Madrid