Senior Backend Engineer

ABOUT EXTEND

Extend offers businesses powerful spend controls and expense workflows that drive efficiency, improve security and visibility, and better manage company spending. Our primary product is a spend and expense management platform that allows SMBs to create on-demand virtual cards, automate reconciliation, and manage employee expense reports. We have built the first virtual card platform of its kind, directly integrated with processors, networks, and the technology that supports banking across the industry. We offer several virtual card products including an app-as-a-service that banks can offer business customers with their existing credit cards, a suite of virtual card APIs for those looking to build custom payment solutions, and we also offer secure connectivity to key banking and payment services that enable 3rd-parties to integrate and embed payments into their software.

VC-funded Extend is headquartered in Manhattan and has recently raised $20m in capital from top fintech investors. With 55 passionate team members and exciting momentum – after launching a new subscription offering over Summer ’25, there’s never been a better time to join our team!

For more information visit paywithextend.com

ABOUT THE TEAM

Our team builds and operates the systems that connect Extend to issuer processors and card networks. These systems support the full card lifecycle—from issuing virtual cards and handling real-time authorizations through clearing and settlement. We turn more than a dozen partners—each with its own domain model, APIs, data formats, and authentication requirements—into one consistent platform. Product Engineering teams across Extend build against that common model instead of handling each partner's differences themselves.

Correctness matters at every layer. Errors here flow into the financial records our customers reconcile against. Many of the partner systems we depend on are difficult to test against reliably. We build the confidence we need ourselves. Security and compliance shape how these systems are designed and operated from the start. SOC 2 and PCI are engineering constraints, not a review gate at the end.

This team is central to Extend's expansion. Every new bank, issuer processor, or network partner adds capabilities to Extend—and new complexity for the platform to absorb. The platform must grow without pushing that complexity into the rest of the product.

Our services run in a distributed microservices architecture on AWS, primarily using Kotlin, Spring Boot, and Postgres. We value experience with comparable distributed systems, cloud infrastructure, relational databases, and backend frameworks more than experience with our exact stack.

At Extend, you'll:

• Design and evolve the abstraction the rest of Extend builds on.
• Build and operate the real-time systems behind card issuance, authorization, and settlement.
• Build the mocks, canaries, and tooling that make partner systems testable.
• Prove our data is right: detect divergence, resolve it deterministically, contain it before it propagates.
• Bring new banks, issuer processors, and network partners online.
• Own problems end to end: design, production reliability, on-call, and the consequences of your own decisions.
• Use AI coding agents heavily. We care about your judgment on the output, not your ability to produce it.

THE CANDIDATE

We don't expect you to have worked in card issuing, payments, or fintech. We do expect you to have worked on backend systems where correctness, reliability, and operational ownership actually mattered — and to be able to tell us specifically about it.

• You've owned a production backend system well past its initial delivery. You were there for the incidents, the redesign pressure, and the point where your own earlier decisions came back at you.
• You've built and operated against external APIs you don't control. Partial failures, retries, idempotency, webhooks, inconsistent responses, no guarantee about what the other side will do.
• You reason rigorously about correctness. Duplicate events, ordering, replay, state machines, reconciliation, auditability. You've had to prove data was right, not just believe it was.
• You have real depth in at least one operational discipline. Observability, integration testing, incident response, or performance work. Something you're the person for.
• You can figure out what a non-technical stakeholder actually needs, as opposed to what they asked for, and explain a technical tradeoff in language that lands with them.

Bonus point

• Event-driven or message-driven architectures, queues, streams, or ledger-like systems.
• Domain-driven design, layered architecture (e.g. Clean Architecture), SOLID principles.
• Functional programming.
• Card networks, issuer processors, authorization, settlement, disputes, or reconciliation.
• PCI, SOC 2, or other regulated financial environments.
• SRE (site reliability engineering) experience.

WHAT WE OFFER

• Competitive compensation package
• Equity for all–our success is your success
• Unlimited vacation–and we want you to use it
• 401K matching
• Flexible work options
• Comprehensive health coverage for you and your family
• Maternity and paternity leave benefits
• Reimbursement for gym memberships
• $5K referral bonus–bring your friends!
• Work with and learn from functional experts across disciplines