Mirrai Careers

Integration Engineer

Light

London Remote Full-time Posted 30+ days ago
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RETIRE THE ERP. Light exists to replace factory-era ERPs with software that feels alive. Our Smart Financial Platform gives modern, global companies superpowers—automated accounting, real-time reporting, and financial flows that move at the speed of the business. We build with our customers, ship fast, and obsess over craft. In a short time, Light has gone from idea to the operating core for leading companies like Lovable, Legora, and Keyshot. People don't just use Light—they enjoy it. We're an early team defining a new software category. Think engineers who love debits and credits, designers who care about reconciliation states, and operators who treat finance as a product. If you're excited to modernize how the world runs money—one workflow at a time—you're in the right place. Backed by world-class investors and advised by industry titans, we're building category-defining products with the freedom to ship ambitiously and own outcomes. Come help us make Light the global default for next-gen finance. THIS INTEGRATIONS ENGINEER ROLE Light is only as powerful as the systems it connects to. Money doesn't move because we say so—it moves because we speak the language of the bank, the e-invoicing network, and the planning tool on the other side, correctly, every time, for every customer entity. This role owns that layer: the interaction surface between Light and the rest of the financial world. You'll build and operate the integrations that let Light plug into multi-tenant banking APIs (J.P. Morgan, HSBC, and peers), global e-invoicing networks, and tax platforms and more. This is backend-heavy, data-integrity-critical work where a dropped message or a silent reconciliation mismatch is not an acceptable outcome. You'll design the abstractions that turn a dozen incompatible partner APIs into one coherent internal model, and you'll keep those abstractions honest as partners change their specs underneath you. What you'll work on: * Bank connectivity. Build against corporate banking and payments APIs—account information, payment initiation, status reporting, FX—across providers like J.P. Morgan Payments and HSBC. Handle the realities of bank integrations: certificate-based and mTLS auth, OAuth flows, ISO 20022 (pain/pacs/camt) and legacy MT formats, sandbox-to-production parity, and rate limits that assume you're a bank, not a startup. * Multi-tenancy done right. Our customers are many legal entities operating in many countries. You'll design integrations where credentials, configuration, and data are isolated per tenant, where onboarding a new entity is a workflow rather than a code change, and where one customer's failure never leaks into another's. * Global e-invoicing. Connect Light to e-invoicing networks and country-specific mandates (Peppol and the growing set of national clearance and reporting regimes). Map between formats, manage compliance-driven edge cases, and keep delivery auditable. * Tax platforms for statutory filing, US sales tax and much more. * Reliability and reconciliation. Idempotency, retries, webhook and polling strategies, dead-letter handling, and end-to-end reconciliation so that what we think happened and what actually happened always agree. YOUR QUALIFICATIONS 4-6 years of experience ideally, plus… You build things. Not prototypes, not demos. Working software in production, doing something real for real users. This is the non-negotiable. You've built integrations against unforgiving external systems. APIs you don't control, that fail in ways the docs don't mention, where correctness is contractual. You know how to defend a system against a partner that returns a 200 with an error in the body. You know banking and payments APIs. Direct, hands-on experience with corporate banking, treasury, or payments APIs is what sets the strongest candidates apart. Experience integrating J.P. Morgan or HSBC specifically—their developer platforms, auth models, and payment and reporting APIs—is highly valuable and a genuine differentiator for this role. Familiarity with ISO 20022, SWIFT, virtual accounts, or open banking is a strong signal. You are excited about AI. You use AI tooling efficiently to improve your work. At Light, a lot of code is written with AI, which means the hard part is increasingly the thinking: deciding what to build, reviewing what comes back, and catching where the model is confidently wrong. You know when AI speeds you up, when it's likely to mislead you, and how to lean on it while staying fully responsible for what ships. You're comfortable across the stack. You don't need to be a specialist in everything, but you can't have a lane you refuse to leave. Our stack is Kotlin and React, and this role leans backend. If you're strong on the backend and curious about the rest, that works. You care about data integrity. You think about the person on the other end and the money moving between them. You notice when a flow is correct but fragile, and you act on it. You ship early and often. Small batches. Learn. Go again. You'd rather put something real in front of a customer than spend another week perfecting it in isolation. BONUS POINTS * Experience in fintech or systems where data integrity is non-negotiable * Familiarity with accounting concepts: debits, credits, reconciliation * Experience with e-invoicing standards or country-specific compliance regimes * Background in high-growth startups where everything was still being figured out OUR TECH STACK We build on AWS, with a Kotlin backend, a React frontend, and infrastructure managed in Terraform. It's a real production system that global finance teams depend on every day. The integration layer you'll own sits squarely in the Kotlin backend, talking to a long list of external partners. You don't need to have used every piece of it. You do need to be comfortable in this kind of environment: real scale, real customers, real stakes. THE GOOD STUFF In addition to being part of a great team and working in a really fun and innovative environment, we offer: * A competitive salary + potential stock options * 25 days of annual leave + public holidays in the country where you are based * Regular socials and company off-sites * A huge opportunity for career growth as you'll help shape a market-defining product THE FAMOUS LAST WORDS Working at Light means you're embarking on an exciting journey to reshape the future of multinational financial operations. Our cheat-code is that we've built something like this before—and are now doing it again, only better. Our goal is to make global finance effortless and empower companies to make informed decisions. Join the rocket ship while it's taking off.

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