Full-stack Engineer - Payments (Spain)

About the role

This role focuses on designing and building the core payment infrastructure for Crossmint's stablecoin and wallet platforms. The work involves creating processor integrations, transaction pipelines, and settlement workflows, along with the APIs that clients use. A key aspect is owning critical financial flows end-to-end, which includes managing failure modes, retry logic, state management, and addressing production edge cases.

The position requires working across the entire stack, with a primary emphasis on backend development. Responsibilities extend to contributing to APIs, dashboards, and client-facing interfaces for payment systems. A crucial part of the job is ensuring data integrity across different providers and blockchain networks, maintaining consistent balances, transaction states, and audit trails even when third-party systems encounter issues.

Success in this role means contributing to architectural decisions by writing design documents and reviewing proposals to guide long-term technical choices. The engineer will also participate in on-call rotations and take ownership of incidents related to the systems they build. As the team expands, there will be opportunities to mentor newer engineers, fostering their growth and development within the company.

The salary for this position ranges from $150,000 to $200,000 USD.

Skills that matter here

• TypeScript: This is a primary programming language used for developing and maintaining production backend systems.
• JavaScript: This is a primary programming language used for developing and maintaining production backend systems.
• Stripe: Experience integrating with this payment processor is required for building the payment infrastructure.
• Adyen: Experience integrating with this payment processor is required for building the payment infrastructure.

Who this role suits

• A person with at least four years of experience building and maintaining production backend systems, especially those involving financial data, payments, or critical transaction infrastructure.
• Someone who understands distributed systems fundamentals, including idempotency, consistency guarantees, failure handling, and asynchronous workflows.
• An individual with hands-on experience integrating with payment processors such as Stripe or Adyen.
• A candidate with exposure to stablecoin infrastructure, crypto payments, wallets, or cross-chain systems, and experience operating financial systems in regulated environments.

From the employer

• Design and build payment infrastructure: processor integrations, transaction pipelines, settlement and reconciliation workflows, and the APIs clients depend on.
• Own critical financial flows end to end, including failure modes, retry logic, state management, and edge cases that matter in production.
• Work across the stack: backend-heavy, but you will contribute to APIs, dashboards, and the interfaces clients use to interact with payment systems.
• Ensure data integrity across providers and chains: balances, transaction states, and audit trails that stay consistent even when third-party systems don't.
• Contribute to architecture decisions: write design docs, review peers' proposals, and help the team make good long-term calls.
• Participate in on-call rotations (paid, once or twice per quarter) and own incidents on the systems you build.
• Help onboard and mentor newer engineers as the team grows.

• 4+ years building and maintaining production backend systems, ideally involving financial data, payments, or transaction-critical infrastructure.
• Strong proficiency in TypeScript or JavaScript (our primary stack), or another typed modern language with willingness to move quickly.
• Solid understanding of distributed systems fundamentals: idempotency, consistency guarantees, failure handling, async workflows.
• Fluent in English, written and spoken.
• Hands-on integration experience with Stripe, Adyen, or similar payment processors.
• Exposure to stablecoin infrastructure, crypto payments, wallets, or cross-chain systems.
• Experience operating financial systems in regulated environments.

• Extensive access to leading AI tools and subscriptions, with AI actively encouraged and integrated into daily workflows.
• Stock options program.
• Two performance reviews annually.
• Unlimited Paid Time Off.
• Parental Leave program.
• Company laptop + Annual home office and productivity stipend.
• Daily stipend for in-office meals and/or commuting to the office.
• Three company-paid off-sites each year.
• Health + Dental insurance fully covered by Crossmint.
• Flexible retribution with tax benefits through Cobee.