Backend Engineer

outpostnow

Greater London

On-site

GBP 90,000 - 130,000

Full time

14 days+

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Benefits offered by this job

Equity

Founding team access

Global mission

Low politics

Job summary

Outpost is hiring a Backend Engineer to build core financial infrastructure from the ground up, focusing on payment flows, tax engines, and multi-currency ledgers. You will help shape architecture and contribute to meaningful fintech products.

Based in London, you will work in person with a small, hands-on team, owning critical components and influencing the technical direction. The role offers equity and the chance to move fast in a well-funded startup.

Qualifications

Fluent in JVM-based backend development with Kotlin.
Experience building payments, tax, or compliance systems is highly desirable.
Strong fundamentals in scalable backend architecture and systems design.

Responsibilities

Write high-quality, maintainable backend code for payments and tax workflows.
Design and implement secure, scalable checkout and reconciliation flows.
Build robust ledger, tax calculation engines, and fraud/risk tooling.
Develop monitoring and alerting for critical financial services.
Collaborate with product and risk teams to align technical requirements.

Skills

Kotlin

JVM

Backend systems

Payments

Tax systems

E-commerce platforms

Job description

Backend Engineer

About Outpost

What if going global was as simple as going local?

Outpost is building the AI global trade engine. The accumulated knowledge of every rule you'd need to sell internationally, turned into infrastructure. Tell us what you're selling. We'll tell you how to sell it everywhere.

We operate as Merchant of Record or Tax of Record across 58+ tax jurisdictions. Full liability transfer, or just the tax layer. We do the analysis, we handle the setup, we absorb the liability.

Sell anything, anywhere. Without compromise.

The Role

This is a Backend Engineer role for someone who wants to build complex financial infrastructure from scratch.

You'll work directly with our engineering leadership to implement payment flows, build tax calculation engines, and create the systems that power international commerce. You'll contribute to product and technical discussions, challenge assumptions, and help guide our technical direction.

We're building the infrastructure that lets businesses sell globally without the usual pain. That means payment processing, multi-currency ledgers, real-time tax calculations, merchant onboarding, and AI-powered compliance tools. Hard problems with real scale.

What You'll Get

Yes, the work is intense. But in return, you'll build critical financial infrastructure that handles hundreds of millions in volume.

You'll have significant input into technical direction, work with a small team of experienced engineers, and shape how Outpost scales. If you want to go deep on payments, tax, and fintech infrastructure, this is the role.

What You’ll Build

Payment processing infrastructure handling hundreds of millions in volume
Robust ledger and reconciliation systems
Tax calculation engines for multiple jurisdictions
Real-time transaction monitoring and risk systems
Merchant onboarding and integration frameworks
Platform connections with major e-commerce systems
AI/LLM powered taxation tools
AI/LLM powered fraud and risk tools

What You’ll Do

Technical Development

Write high-quality, maintainable code
Implement core payment and financial systems
Build secure, scalable backend services
Contribute to system architecture discussions
Help establish engineering best practices

System Design & Implementation

Design and build robust payment processing flows
Implement internal ledger and reconciliation systems
Create merchant integration frameworks
Develop automated monitoring and alerting
Handle secure financial data processing

Cross-functional Collaboration

Work with product team to refine technical requirements
Contribute to API design and implementation
Collaborate with risk and compliance on system requirements

Example Projects

Implement a multi-currency ledger that handles real-time reconciliation
Create the tax calculation engine for a new jurisdiction
Design the merchant onboarding flow and integration framework
Build AI-powered tools for automated tax classification
Implement real-time fraud detection and risk scoring
Create automated reconciliation systems that catch discrepancies before they become problems

What We’re Looking For

Ideal background:

Fluency in a JVM-based language, preferably Kotlin
Track record of implementing complex backend systems
Strong engineering fundamentals and coding practices
Bonus: experience building financial, payments, tax, or compliance systems
Bonus: familiarity with e-commerce platforms

Signals we care about:

You write high-quality code and care about maintainability
You can design systems, not just implement them
You're comfortable with ambiguity and figuring things out
You contribute to technical discussions and challenge assumptions
You want to build from scratch, not maintain existing systems
Bias for action. You ship, you learn, you iterate

What this role is not:

Not maintaining existing systems. You'll build from scratch
Not a role where you wait to be told what to do
Not someone who needs heavy process or detailed specs to be effective
Not pure execution without input into technical direction

Why This Role Is Different

Most backend roles are about maintaining or extending existing systems. This role is about building complex financial infrastructure from the ground up.

You'll tackle challenges like managing multiple currency ledgers, handling card payment flows, building automated reconciliation systems, and creating AI-powered tax tools. You'll have significant input into our technical direction.

If you're excited about building complex payment systems and want to shape the future of international commerce, this is the role.

Outpost Team

Our team were leaders at Revolut, Airwallex, Adyen and Wayflyer, and we're backed by top-tier investors who have built or backed some of the world's leading fintechs.

What We Offer