Full-Stack Engineer

TypeScript / Effect / AI-Native

• Full-Time
• Copenhagen (in-office)

About Franklin

Franklin is a Danish B2B fintech company building the financial platform modern e-commerce companies rely on to grow. One place to manage spend, payments, cash flow, and financial operations without friction. Founded in 2023, backed by world-class investors, already the preferred platform in Denmark, and now going European.

We're building an AI-native platform from day one. Our engineers use cutting-edge AI tools in their daily workflow, our product runs on LLM-powered receipt matching and categorization, and the next phase is fully agentic bookkeeping, autonomous AI agents that handle categorization, VAT, reconciliation, and financial operations without human input. This isn't "AI features", we’re building an AI-native company.

The role

We're not looking for someone who writes code. We're looking for an engineer who thinks in systems, someone who can look at a messy financial domain, design the right solutions, and build infrastructure that scales across markets, payment rails, and accounting standards.

You'll work directly with Johan (CTO) and have real influence on Franklin's technical direction. Small team, flat structure, and hard problems. You'll own architecture decisions, design AI pipelines, and shape how we build an autonomous financial platform, not just ship features on top of one.

What you'll architect and build

• AI-native financial infrastructure: Design and build the pipelines behind receipt matching, transaction categorization, and agentic bookkeeping. Choose the right models, design the right data flows, handle edge cases at scale.
• System design for multi-market expansion: Reason about what breaks when we add new payment rails, accounting standards, and compliance requirements across EU markets. Design abstractions that don't collapse.
• Effect-based architecture: Own architectural decisions in our Effect + Next.js stack. Design typed, composable services with proper error handling, dependency injection, and testability. Lead the ongoing Rails → Next.js migration.
• API and integration design: Architect integrations with accounting platforms (Exact, Odoo, Quickbooks, Xero), payment providers (NIUM), and e-commerce systems. Design APIs that are clean, extensible, and correct.
• Data modeling for financial systems: Design schemas and transaction models for a platform handling real money across multiple currencies, entities, and regulatory regimes.

The stack

• Frontend: TypeScript, Next.js, React, Tailwind CSS, Storybook
• Backend: TypeScript with Effect (primary), Next.js API routes, legacy Ruby on Rails being actively phased out
• Testing: Vitest and Playwright
• Mobile: Expo + React Native, TypeScript with Effect, Effect RPC
• Data: PostgreSQL on Neon (serverless, EU)
• AI: Codex and Claude for engineering workflow; Gemini + OpenAI powering product features (receipt OCR, categorization, agentic bookkeeping)
• Infra: Vercel, Trigger.dev, Sentry, AWS, Neon
• Monorepo: Bun, Turborepo

What's on the near-term roadmap

• Agentic bookkeeping: autonomous AI agents for categorization, VAT, reconciliation
• Improved AI receipt matching: LLM + OCR pipeline, continuously improving accuracy and coverage
• Bill Pay: outbound payments via SWIFT, SEPA and DKK local rails with automated bookkeeping
• Mobile via Expo (shared codebase between Android/iOS)
• Geo expansion: accounting integrations across EU markets
• Rails → Effect/Next.js migration: architect the transition, not just port the code

We expect you to

• Think in systems, not tickets. You see the architecture, not just the features.
• Be strong in TypeScript, Next.js, React, and Tailwind, and have opinions about how to use them well
• Be comfortable designing and working with AI/LLM pipelines. Agentic engineering, workflow optimisation, and building reliable systems on top of probabilistic outputs
• Know how to model data for transactional financial systems. PostgreSQL, schemas that handle real money, audit trails, multi-currency
• Have shipped API integrations, webhooks, and REST APIs in production, and thought carefully about how they should be designed
• Write clearly. Code, PRs, architecture docs, Slack. Written clarity is how decisions get made here.
• Have low ego and high standards. You take feedback well but push back thoughtfully

Bonus points

• Built or contributed to AI/LLM-backed product features, especially in domains where accuracy matters (finance, healthcare, legal)
• Direct Effect experience
• Experience in fintech or payments infrastructure (NIUM, Adyen, Stripe Issuing, Marqeta)
• Led a migration from a legacy stack (Rails → TS, monolith → monorepo, etc.)
• Designed systems for multi-market or multi-tenant environments
• React Native / Expo experience
• Familiarity with Trigger.dev, Neon, Vercel, or AWS

What we offer

• A seat at the architecture table. You're not implementing someone else's design
• Direct line to the CTO, no middlemen
• AI-native engineering culture. Codex, Claude, Cursor, and whatever else makes you faster. We don't gatekeep tools.
• Equity in Franklin (warrant program)
• Top-notch gear, incl. MacBook, and whatever else you need
• Office at Købmagergade 26C in the heart of Copenhagen, in-office by default
• 5 weeks paid vacation, great lunch scheme, generous expense allowance every month

How we work

• Ship small, fast releases over big, perfect launches. Make it work → make it pretty → make it fast.
• Extreme ownership, spot a problem, unclear who owns it? You own it.
• Radical transparency, honest, direct, delivered with kindness.
• AI-native by default. If a task can be automated or augmented, it should be.
• Office by default. We're building something hard, that demands tight collaboration and high speed.